Phase 988: document sparse ACK diagnostics embed extract (v0.8.955)

Update roadmap, testing, modules index, and release notes for mesh stability
UI sparse ACK diagnostics keys refactor. Phase 988 complete; Phase 989 active.

Co-authored-by: Cursor <[email protected]>

release_notes/RELEASE_v0.8.955.md

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+# Release v0.8.955 — Phase 988: Mesh Stability UI Sparse ACK Diagnostics Embed Keys Extract
+
+**Date:** 2026-06-05
+**Type:** Non-breaking refactor — mesh stability UI parity hardening
+
+## Summary
+
+Phase 988 extracts diagnostics panel sparse ACK cursor list embed from `app.js` into
+dedicated modules with identical HTML and copy.
+
+## New Modules
+
+### `pearcord-platform/mesh-stability-ui-sparse-ack-diagnostics-keys.js`
+
+- 2 row field keys: channelId, offset
+- 2 embed part keys: label, cursorList
+- `buildMeshStabilitySparseAckDiagnosticsSnapshot()`
+
+### `apps/pearcord/ui/mesh-stability-ui-sparse-ack-diagnostics.js`
+
+- `formatMeshStabilitySparseAckCursorLine()`, `buildMeshStabilitySparseAckDiagnosticsEmbedHtml()`
+
+## Test Coverage
+
+- `smoke-mesh-stability-ui-sparse-ack-diagnostics-build.cjs` — keys registry + embed HTML + app.js wire checks
+- `smoke-phase988-boot-gate.cjs` — version check (0.8.955)
+- `smoke-agentctl-mesh-stability-ui-sparse-ack-diagnostics-journey-stub.cjs` — agentctl integration stub
+- `test:mesh-stability-stats` — extended with sparse ACK diagnostics snapshot assertions
+- `test:gossip-rpc-pull-unit` — extended with sparse ACK diagnostics embed part keys
+- `test:ci-phase988` — full CI bundle
+
+## Version
+
+`0.8.954` → `0.8.955`