fix: register enabled extensions for agent on integration use/upgrade (#2949)

* fix: register enabled extensions for agent on integration install/upgrade

install and upgrade only set up the integration's own core commands; only
switch re-registered the enabled extensions' commands for the target agent.
A second integration added via install (or refreshed via upgrade) was
therefore silently missing the extension commands the existing agents
already had (e.g. the bundled agent-context extension).

Extract switch's registration into a shared _register_extensions_for_agent
helper and call it from install and upgrade too, so every installed agent
ends up with every enabled extension's commands — full parity with switch.

Closes #2886

* test: pin skills-mode secondary-agent registration; document #2948 limitation

Extension skill rendering is scoped to the active agent (init-options track a
single ai / ai_skills pair), so a skills-mode agent registered while not active
(e.g. Copilot --skills installed as a secondary integration) gets command files
rather than skills. install/upgrade match extension add here; only switch
renders skills, because it activates the target first.

Add a regression test pinning this behavior and document the limitation on the
shared helper. Per-agent skills parity is tracked separately in #2948.

* fix: don't re-render the active agent's skills when registering a non-active agent

register_enabled_extensions_for_agent runs an active-agent-scoped skills pass
(_register_extension_skills resolves the skills dir from init-options["ai"],
ignoring the passed agent). Routing install/upgrade of a secondary integration
through it re-rendered the *active* skills-mode agent's extension skills as a
side effect — resurrecting skill files the user had deliberately deleted. Gate
the skills pass on the target being the active agent; switch is unaffected
because it activates the target first.

Also harden the skills-mode install test (assert a core skill so --skills is
load-bearing, drop a vacuous registered_skills assertion) and add a regression
test. Surfaced by review of the PR; skills parity for non-active agents stays
tracked in #2948.

* refactor: share the extension-op scaffold and run (un)registration post-commit

Review cleanups, no behavior change on the success path:

- Extract the best-effort ExtensionManager scaffold (lazy import, instantiate,
  except -> _print_cli_warning) into _best_effort_extension_op. Both
  _register_extensions_for_agent and a new _unregister_extensions_for_agent
  delegate to it, removing the duplicate block left inline in switch.
- Invoke the best-effort extension registration AFTER the install/switch/upgrade
  try/except has committed, so a failure in it can never trigger the rollback
  (install and switch teardown on except).

* docs: clarify extension registration parity scope

* fix(integrations): defer extension registration until use

* fix(tests): remove redundant shutil import

* fix(integrations): backfill extensions for installed switch targets

src/specify_cli/integrations/_migrate_commands.py

@@ -27,12 +27,14 @@ from ._helpers import (
     _get_speckit_version,
     _read_integration_json,
     _refresh_init_options_speckit_version,
+    _register_extensions_for_agent,
     _remove_integration_json,
     _resolve_integration_options,
     _resolve_integration_script_type,
     _resolve_script_type,
     _set_default_integration,
     _set_default_integration_or_exit,
+    _unregister_extensions_for_agent,
     _update_init_options_for_integration,
     _write_integration_json,
 )
@@ -120,6 +122,14 @@ def integration_switch(
             parsed_options=parsed_options,
             refresh_templates_force=force,
         )
+        _register_extensions_for_agent(
+            project_root,
+            target,
+            continuing=(
+                "The integration switch succeeded, but installed extensions may "
+                "need re-registration."
+            ),
+        )
         console.print(f"\n[green]✓[/green] Default integration set to [bold]{target}[/bold].")
         raise typer.Exit(0)
 
@@ -171,19 +181,11 @@ def integration_switch(
 
         # Unregister extension commands for the old agent so they don't
         # remain as orphans in the old agent's directory.
-        try:
-            from ..extensions import ExtensionManager
-
-            ext_mgr = ExtensionManager(project_root)
-            ext_mgr.unregister_agent_artifacts(installed_key)
-        except Exception as ext_err:
-            _print_cli_warning(
-                "clean up extension artifacts for",
-                "integration",
-                installed_key,
-                ext_err,
-                continuing="Continuing with integration switch; old extension artifacts may need manual cleanup.",
-            )
+        _unregister_extensions_for_agent(
+            project_root,
+            installed_key,
+            continuing="Continuing with integration switch; old extension artifacts may need manual cleanup.",
+        )
 
         # Clear metadata so a failed Phase 2 doesn't leave stale references
         installed_keys = [installed for installed in installed_keys if installed != installed_key]
@@ -270,22 +272,6 @@ def integration_switch(
             parsed_options=parsed_options,
         )
 
-        # Re-register extension commands for the new agent so that
-        # previously-installed extensions are available in the new integration.
-        try:
-            from ..extensions import ExtensionManager
-
-            ext_mgr = ExtensionManager(project_root)
-            ext_mgr.register_enabled_extensions_for_agent(target)
-        except Exception as ext_err:
-            _print_cli_warning(
-                "register extension artifacts for",
-                "integration",
-                target,
-                ext_err,
-                continuing="The integration switch succeeded, but installed extensions may need re-registration.",
-            )
-
     except Exception as exc:
         # Attempt rollback of any files written by setup
         try:
@@ -333,6 +319,15 @@ def integration_switch(
         )
         raise typer.Exit(1)
 
+    # Re-register extension commands for the new agent so previously-installed
+    # extensions are available in it. Done after the try/except (the switch has
+    # committed) so this best-effort step can never trigger the rollback above.
+    _register_extensions_for_agent(
+        project_root,
+        target,
+        continuing="The integration switch succeeded, but installed extensions may need re-registration.",
+    )
+
     name = (target_integration.config or {}).get("name", target)
     console.print(f"\n[green]✓[/green] Switched to integration '{name}'")
 
@@ -496,5 +491,17 @@ def integration_upgrade(
         if stale_removed:
             console.print(f"  Removed {len(stale_removed)} stale file(s) from previous install")
 
+    # Re-register enabled extensions for the upgraded agent so its extension
+    # commands are (re)created — including agents installed before this
+    # back-fill existed. Mirrors switch for command registration; see #2886.
+    # Done after the upgrade has fully settled (Phase 2 included) and outside
+    # the try/except above so this best-effort step cannot affect upgrade
+    # success.
+    _register_extensions_for_agent(
+        project_root,
+        key,
+        continuing="The integration was upgraded, but installed extensions may need re-registration.",
+    )
+
     name = (integration.config or {}).get("name", key)
     console.print(f"\n[green]✓[/green] Integration '{name}' upgraded successfully")