feat(extensions): add bundled bug triage workflow extension (#2871)

* feat(extensions): add bundled bug triage workflow extension (#2870)

Add a bundled 'bug' extension providing a three-stage bug triage workflow:

- speckit.bug.assess: triage a bug report (pasted text or URL), locate
  suspected code paths, and propose a remediation
- speckit.bug.fix: apply the proposed remediation and record what changed
- speckit.bug.test: validate the fix and record the verification result

Each bug gets its own directory under .specify/bugs/<slug>/ with one
Markdown report per stage (assessment.md, fix.md, test.md). The slug is
the only handle the three commands share; existing bug directories are
never overwritten.

Mirrors the layout of the existing bundled extensions (git, agent-context):

- extensions/bug/extension.yml, README.md, commands/
- extensions/catalog.json: register 'bug' (alphabetical, between
  agent-context and git)
- pyproject.toml: add wheel mapping to specify_cli/core_pack/extensions/bug

Closes #2870

* address Copilot review on #2871

- speckit.bug.assess.md: drop POSIX-specific 'mkdir -p' example;
  reword the prerequisite to describe the requirement (ensure BUG_DIR
  exists) without assuming a specific shell.
- speckit.bug.fix.md: fix the slug-resolution fallback wording. It
  listed '.specify/bugs/*/assessment.md' but then keyed off whether
  'exactly one bug directory' existed; now it correctly keys off whether
  exactly one matching 'assessment.md' was found and uses the slug from
  its parent directory.
- tests/extensions/bug/test_bug_extension.py: add a smoke test analogous
  to the agent-context extension's coverage. Validates the bundled
  layout, catalog registration, '_locate_bundled_extension("bug")'
  resolution, and that 'ExtensionManager.install_from_directory' installs
  the three commands.

All 333 tests in tests/extensions/, tests/test_extensions.py, and
tests/test_extension_registration.py pass.

* address Copilot review on #2871 (round 2)

- Import _locate_bundled_extension from the public 'specify_cli'
  package (it is re-exported in __init__.py) instead of the private
  'specify_cli._assets' module, so the test does not depend on internal
  module layout.
- Clarify module docstring: install_from_directory is called with
  register_commands=False, so commands are copied and recorded in the
  installed manifest but not registered with AI agents. Wording updated
  to avoid implying otherwise.

* address Copilot review on #2871 (round 3)

- tests/extensions/bug/test_bug_extension.py: read extension.yml as
  UTF-8 explicitly to avoid platform-dependent default encoding (notably
  on Windows). Matches how the README is read in the same module.
- extensions/bug/commands/speckit.bug.assess.md: add a 'Safety When
  Fetching URLs' section. Instructs the agent to treat fetched page
  content as untrusted input (no obeying embedded prompt-injection
  directives), forbids supplying credentials/secrets that a page asks
  for, scopes the fetch to the URL the user provided (no following
  redirects to other resources), and requires suspicious content to be
  quoted verbatim under an 'Unverified' heading rather than acted on.
- extensions/catalog.json: bump 'updated_at' to today (2026-06-05) so
  consumers that cache by this field invalidate when 'bug' is added.
- extensions/bug/README.md: minor grammar fix ('a reproduction that was
  not actually performed').

All 251 tests in tests/extensions/bug/, tests/test_extensions.py, and
tests/test_extension_registration.py pass.

* speckit.bug.assess: add URL Trust Policy for fetched bug-report URLs

Builds on the 'Safety When Fetching URLs' section by adding a tiered
classification rule the agent applies before any fetch:

1. Refuse outright (no fetch, no prompt) for non-http(s) schemes,
   loopback, link-local, RFC1918 private space, and known cloud
   instance-metadata endpoints (169.254.169.254, metadata.google.internal,
   100.100.100.200, metadata.azure.com). This closes the SSRF /
   internal-recon vector opened by 'paste any URL'.
2. Fetch silently for an explicit allowlist of widely-used public
   bug-report sources (github, gitlab, bitbucket, atlassian.net, linear,
   stackoverflow/stackexchange, sentry). This preserves the paste-a-URL
   ergonomics the workflow is built for.
3. Otherwise prompt once in interactive mode (default 'no', naming the
   resolved host explicitly); in automated mode skip the fetch and
   record '[UNVERIFIED - fetch skipped: host not on safe list: <host>]'
   in assessment.md so a human can decide later.

In every case, assessment.md records the verbatim URL, the resolved host,
and which branch of the policy was taken (allowlisted /
confirmed-by-user / auto-refused: <reason>) so the per-bug directory's
audit trail is complete. Preflight HEAD probes are explicitly forbidden
since the probe itself is the request the policy gates.

Execution step 1 now defers to the policy before fetching.

* speckit.bug.assess: remove 'post-redirect-resolution' inconsistency

The URL Trust Policy explicitly forbids following redirects, but the
audit-trail bullet asked the agent to record the host
'post-redirect-resolution', which contradicted that rule and could lead
agents to follow redirects unintentionally to determine what to log.

Reword both call sites to refer to the host parsed from the URL the user
supplied (no resolution implied):

- Tier-3 interactive prompt: '...naming the host parsed from the URL
  explicitly...'
- Recorded fields: 'The host parsed from that URL (no redirect following
  - see the rule above).'

No behavior change; clarification only.

tests/extensions/bug/test_bug_extension.py

@@ -0,0 +1,113 @@
+"""Tests for the bundled ``bug`` extension.
+
+Validates:
+- Bundled layout (manifest, README, three command files)
+- Catalog registration
+- Wheel/source-checkout resolution via ``_locate_bundled_extension``
+- Install via ``ExtensionManager.install_from_directory`` copies the three
+  command files and records them in the installed manifest (command
+  registration with AI agents is exercised separately and not asserted here)
+"""
+
+from __future__ import annotations
+
+import json
+from pathlib import Path
+
+import yaml
+
+from specify_cli import _locate_bundled_extension
+
+
+PROJECT_ROOT = Path(__file__).resolve().parent.parent.parent.parent
+EXT_DIR = PROJECT_ROOT / "extensions" / "bug"
+
+EXPECTED_COMMANDS = {
+    "speckit.bug.assess",
+    "speckit.bug.fix",
+    "speckit.bug.test",
+}
+
+
+# ── Bundled extension layout ─────────────────────────────────────────────────
+
+
+class TestExtensionLayout:
+    def test_extension_yml_exists(self):
+        assert (EXT_DIR / "extension.yml").is_file()
+
+    def test_extension_yml_has_required_fields(self):
+        manifest = yaml.safe_load(
+            (EXT_DIR / "extension.yml").read_text(encoding="utf-8")
+        )
+        assert manifest["extension"]["id"] == "bug"
+        assert manifest["extension"]["name"] == "Bug Triage Workflow"
+        assert manifest["extension"]["author"] == "spec-kit-core"
+        commands = {c["name"] for c in manifest["provides"]["commands"]}
+        assert commands == EXPECTED_COMMANDS
+
+    def test_readme_exists(self):
+        readme = EXT_DIR / "README.md"
+        assert readme.is_file()
+        text = readme.read_text(encoding="utf-8")
+        assert "Bug Triage Workflow Extension" in text
+
+    def test_command_files_exist(self):
+        for name in EXPECTED_COMMANDS:
+            cmd = EXT_DIR / "commands" / f"{name}.md"
+            assert cmd.is_file(), f"Missing command file: {cmd}"
+
+
+# ── Catalog registration ─────────────────────────────────────────────────────
+
+
+class TestCatalogEntry:
+    def test_catalog_lists_bug_as_bundled(self):
+        catalog = json.loads(
+            (PROJECT_ROOT / "extensions" / "catalog.json").read_text(encoding="utf-8")
+        )
+        entry = catalog["extensions"]["bug"]
+        assert entry["bundled"] is True
+        assert entry["id"] == "bug"
+        assert entry["author"] == "spec-kit-core"
+
+
+# ── Bundle resolution ────────────────────────────────────────────────────────
+
+
+class TestBundleResolution:
+    def test_locate_bundled_extension_finds_bug(self):
+        located = _locate_bundled_extension("bug")
+        assert located is not None
+        assert (located / "extension.yml").is_file()
+
+
+# ── Install ──────────────────────────────────────────────────────────────────
+
+
+class TestExtensionInstall:
+    def test_install_from_directory(self, tmp_path: Path):
+        from specify_cli.extensions import ExtensionManager
+
+        (tmp_path / ".specify").mkdir()
+        manager = ExtensionManager(tmp_path)
+        manifest = manager.install_from_directory(EXT_DIR, "0.9.0", register_commands=False)
+
+        assert manifest.id == "bug"
+        assert manager.registry.is_installed("bug")
+
+        # All three command files are copied into the installed extension dir
+        installed = tmp_path / ".specify" / "extensions" / "bug"
+        for name in EXPECTED_COMMANDS:
+            assert (installed / "commands" / f"{name}.md").is_file()
+
+    def test_install_command_names(self, tmp_path: Path):
+        """The installed manifest exposes the expected command names."""
+        from specify_cli.extensions import ExtensionManager
+
+        (tmp_path / ".specify").mkdir()
+        manager = ExtensionManager(tmp_path)
+        manifest = manager.install_from_directory(EXT_DIR, "0.9.0", register_commands=False)
+
+        names = {c["name"] for c in manifest.commands}
+        assert names == EXPECTED_COMMANDS