feat(presets): add opt-in constitution-sync preset (#3873)

* feat(presets): add opt-in constitution-sync preset

Follow-up to #3790, which removed the consistency-propagation pass from the
core /constitution command in favor of runtime resolution. Teams that treat
materialized plan/spec/tasks templates as reviewed, committed artifacts lost
the auto-sync of amended constitutional guidance on a non-forced upgrade.

Add a bundled, opt-in `constitution-sync` preset that restores that behavior
via a wrap-strategy override of speckit.constitution (composes on {CORE_TEMPLATE}
so it stays forward-compatible). It only writes into the project's own
.specify/templates scaffolds and installed command files, never into
stack-owned template layers.

- presets/constitution-sync/: preset.yml (requires >=0.14.4), wrap command,
  README documenting the tension between auto-propagation and the resolution stack
- presets/catalog.json: bundled entry
- docs/upgrade.md: document the 0.14.4 behavior change and the opt-in
- tests/test_presets.py: structural + composition coverage (TestConstitutionSyncPreset)

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* fix(presets): ship constitution-sync in wheel, clarify scope guard, assert composition

Address review feedback on #3873:

- pyproject.toml: force-include presets/constitution-sync into the wheel's
  core_pack so `_locate_bundled_preset` resolves it in a released install; the
  bundled advertisement was otherwise unshippable.
- tests/contract/test_wheel_bundled_presets.py: new contract test asserting
  every bundled preset in presets/catalog.json is force-included (guards lean too).
- commands/speckit.constitution.md: explicitly state the propagation section
  supersedes the core Scope Guard, which otherwise says dependent templates are
  not modified here.
- tests/test_presets.py: assert resolve_content substitutes {CORE_TEMPLATE} and
  the effective command embeds both the core body and the sync pass.

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* test(presets): parse frontmatter as YAML in constitution-sync wrapper test

Address review feedback on #3873: assert `strategy: wrap` structurally by
parsing the Markdown frontmatter as YAML (instead of a substring match that
could false-positive on body text), and assert {CORE_TEMPLATE} in the body
section only.

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* docs(presets): reframe constitution-sync README around behavior and caveats

Rework the preset's user-facing docs to describe what it does, what it does
not do, and the caveats you take on — rather than leading with version/origin
history. The preset stack is the project's forward direction, so the README no
longer positions this as "restoring pre-0.14.4 behavior."

Also make the edit-in-place vs. composition conflict explicit and consistent
across the wrapper command and docs: propagation into command files/templates
that are provided or wrapped by a preset/extension is clobbered on stack
reconciliation (integration use/upgrade, preset/extension install/remove), so
the wrapper restricts propagation to project-local artifacts the team owns.

- README: forward-looking "What it does / does not do / When to use / Caveats"
- speckit.constitution.md: step 4 no longer hand-edits composed command files;
  closing caveat covers command files too
- docs/upgrade.md: note the composition-model conflict in the opt-in section
- tests: assert the updated closing-caveat wording

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* docs(presets): tweak constitution-sync README default-behavior wording

Phrase the default-behavior note as "the current version of Spec Kit" and
rewrap the opening paragraph.

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* docs(presets): keep emphasis spans on one line in constitution-sync README

Avoid **bold** spans broken across soft line breaks (runtime resolution,
reviewed committed artifacts) so they render consistently.

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* docs(presets): refocus constitution-sync README on what it restores

Reframe the intro around what the preset restores and what the user opts
into, rather than describing current Spec Kit default behavior. Be honest
that propagation was removed deliberately (duplicates the source of truth,
fights composition) and this preset knowingly reintroduces it and its
tradeoffs. Minor flow fixes (comma splice, terse bullet).

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* docs(upgrade): de-pin version from /constitution behavior-change section

The upgrade guide always describes the latest version, so hard-pinning
"0.14.4" in the heading and "Starting in 0.14.4" in the body added no
value. Keep the #3790 provenance link and the "no longer propagates"
framing; the machine-readable version gate stays in preset.yml.

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* docs(upgrade): clarify non-breaking nuance and presets direction

Note that the /constitution scope change is only noticeable if you relied
on the old edit-in-place behavior, and add the forward-looking framing:
presets and extensions — not in-place file edits — are how Spec Kit now
governs, versions, and audits shared assets across repositories.

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docs/upgrade.md

@@ -208,6 +208,74 @@ Restart your IDE to refresh the command list.
 
 ---
 
+## Behavior change: `/constitution` no longer propagates into templates
+
+The `/constitution` command ([#3790](https://github.com/github/spec-kit/pull/3790)) is scoped to
+its own artifact. It updates
+`.specify/memory/constitution.md` and writes a Sync Impact Report, and **no longer edits**
+`plan-template.md`, `spec-template.md`, `tasks-template.md`, installed command files, or
+guidance docs.
+
+### Why
+
+Spec Kit uses **runtime resolution**: `plan`, `tasks`, and `analyze` read
+`.specify/memory/constitution.md` live on every run, and `analyze` is the dedicated drift
+checker. The governed templates carry a pointer, not a copy — `plan-template.md` ships
+`[Gates determined based on constitution file]`, and `/plan` fills that section from the live
+constitution each run. Propagation duplicated the single source of truth and fought the
+preset/override composition system (a `replace` preset shadows an edited core template).
+
+More broadly, presets and extensions — not in-place file edits — are how Spec Kit now governs
+shared assets. Composing policy through the resolution stack keeps it centrally owned, versioned,
+and auditable across repositories, instead of frozen into per-repo copies no core team can see.
+
+### Is this a breaking change for existing projects?
+
+**No — your workflow keeps working.** You would only notice a difference if you relied on
+`/constitution` editing those files in place. The templates are scaffolds, not authorities. When you
+run `/plan`, it copies the template into a per-feature `plan.md` and re-derives the Constitution
+Check from the live constitution; `/analyze` validates against it. Even if a previous
+`/constitution` run materialized concrete gate text into `.specify/templates/plan-template.md`,
+the live constitution remains the source of truth at runtime.
+
+On a **non-forced upgrade**, a materialized template is *preserved* (its hash diverges from the
+recorded managed copy, so the refresh treats it as a customization and does not overwrite it).
+Nothing regresses.
+
+### Optional cleanup — return to the runtime pointer
+
+A frozen, pre-filled Constitution Check is a slightly misleading scaffold and can bias the first
+`/plan` pass. To move fully back to runtime resolution, reset the section body in
+`.specify/templates/plan-template.md` to the pointer:
+
+```text
+## Constitution Check
+
+*GATE: Must pass before Phase 0 research. Re-check after Phase 1 design.*
+
+[Gates determined based on constitution file]
+```
+
+Leave the rest of the file untouched. This is cleanup, not a required migration.
+
+### Keeping the old behavior (opt-in)
+
+If your team treats the materialized templates as **reviewed, committed artifacts** and wants
+`/constitution` to keep propagating, install the bundled **`constitution-sync`** preset:
+
+```bash
+specify preset add constitution-sync
+```
+
+It wraps the core `/constitution` command and re-adds the propagation pass. It does **not** edit
+versioned preset- or extension-provided templates or command files (those are owned by their
+packages and are recomposed on reconciliation). Note that this edit-in-place propagation model
+conflicts with the composition model used by the rest of the SDD commands when they are
+preset/extension-managed — see the "Interaction with the resolution stack" section in
+`presets/constitution-sync/README.md` for the tradeoffs and when to prefer the default instead.
+
+---
+
 ## Common Scenarios
 
 ### Scenario 1: "I just want new slash commands"