Tighten maintenance structure and deployment hygiene

[Ankit6149]

Issue linkage

Part of #340

This is a bounded follow-up maintenance slice discovered during the live post-closeout re-audit. Creating another hygiene tracker would add noise.

Outcome

• makes docs/README.md the complete documentation map and explicitly separates current authorities from historical pointers;
• retires the stale implementation ledger from active execution authority and routes Personal Alpha status to current truth;
• removes the completed one-shot reconciliation checkpoint workflow after repo-hygiene-2026-10-05 was verified;
• removes obsolete hard-coded branch-retirement exceptions so future pruning deletes only merged or zero-ahead refs;
• makes master the sole automatic Vercel branch;
• changes the Vercel ignored-build guard so a master commit with no frontend changes since the previous successful deployment is skipped instead of producing another function-heavy production deployment;
• preserves explicit [vercel-preview] checkpoints and fails open to a build whenever the guard cannot prove the frontend is unchanged.

Scope boundary

No product feature, UI, domain contract, connector, inference route, persistence model, or GP2 acceptance behavior changes. No broad refactor. No Playwright.

Current-truth impact

• No capability/runtime claim changes
• docs/CAPABILITY_MATRIX.md does not require a capability change
• docs/CURRENT_EXECUTION_STATE.md remains the execution authority; this PR removes a competing stale status source rather than creating another one
• README/public/AI product claims do not change
• [P0][Repo Hygiene] Reconcile GitHub, docs, source tree, and production truth #340 already owns the remaining external/admin hygiene boundary

Planned ≠ coded ≠ merged ≠ deployed ≠ accepted. This PR changes repository/documentation/deployment-control structure only.

Validation

• documentation map covers every current top-level Markdown file in docs/
• branch-hygiene diff remains fail-closed for unproven unique work
• Vercel guard continues builds when frontend changes are detected or when Git comparison cannot safely prove equivalence
• Normal repository CI passes
• Production build passes
• No Playwright dependency or Playwright-based capture path introduced

Deployment / acceptance

• Deployment verification is required after merge because this PR changes the deployment-control code itself; the branch produced only CANCELED non-production deployment records, and the merged master should receive one normal production build.
• Exact post-merge deployment/status evidence to be recorded before calling this slice complete.

Remaining work / blockers

External GitHub About/topics/governance controls, old Vercel deployment deletion/storage verification, and #44 explicit viewport/200% zoom evidence remain outside this repository-code slice.

[vercel]

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1 Skipped Deployment

Project	Deployment	Actions	Updated
signal-flow-studio	Ignored		Oct 5, 2026 4:59pm UTC

[Ankit6149]

Post-merge deployment verification:

• merged SHA: 3855358cf7e284a2999c92c7b2f16f7938e5c21e
• production deployment: dpl_7oEYgZ64UnkqBo8Z52Yt7oPMvwua
• target: production
• state: READY
• production aliases include signal-flow-studio.vercel.app
• the maintenance branch was automatically removed after merge
• branch inventory returned to master + reserved Gate-C branch only
• [RESERVED — DO NOT MERGE] Gate C GP2 acceptance event #315 returned to being the only open PR

Branch-side Vercel evidence for #406: all nine maintenance-branch deployment records were CANCELED rather than READY previews.