Reconcile FEATURES.md and PROJECT-MAP.md with the current generator

[Jason-Vaughan]

What

• FEATURES.md: restore the current scaffold — stable file.js#symbolName anchor format, section named Governance / Engines.
• PROJECT-MAP.md: add the missing Tangle-Shared doc group.
• Resolve the three auto-stubbed TBD entries and fill every <!-- describe --> placeholder in both files.
• CHANGELOG under ### Internal.

Why

Both files were committed in the 2026-07-06 wrap (#84) from a superseded TangleClaw scaffold, while newer regenerated copies sat untracked in the working tree — they collided on the next git pull.

Rather than guess which side won, I checked the generator: TangleClaw/lib/projects.js (FEATURE_INDEX_TEMPLATE) emits exactly the untracked copies. The committed ones are stale in two specific ways:

• FEATURES.md documented the file.js:line pointer format, which the generator has since abandoned in favor of stable file.js#symbolName anchors — the template's own reasoning is that line pointers rot because nothing re-verifies them. A map instructing future sessions to write rotting pointers is worse than no map.
• PROJECT-MAP.md predated the Tangle-Shared group (created 2026-07-29, 5 members — confirmed live against the TangleClaw groups API, not inferred from the file).

Notes on judgment calls

• The ARCHITECTURE.md stub gets no feature entry. It is a design document, not a feature; it was stubbed only because a PR touched the file. Inventing a feature to clear a checkbox would put a wrong entry in the index permanently.
• FEATURES.md is still sparse — Server / API and Governance / Engines are empty. That is the pre-existing state, not something this PR removed; the serve endpoint and delegate MCP server have no entries yet. Filling the index properly is separate work and I did not smuggle it in here.
• The generator seeds these files but never overwrites them, so this drift would not have self-corrected.

Test plan

• Both files diffed against FEATURE_INDEX_TEMPLATE in TangleClaw/lib/projects.js — headers and section names now match.
• Tangle-Shared verified as a real, live group via the TangleClaw API before adding it.
• No <!-- describe --> or TBD markers remain in either file.
• Suite green: 495 tests, 17 skipped (docs-only change; run as a regression check).

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