fix(dashboard): close 7 review findings on extended-status hardening

Settings inheritance (high):
  - Restored the value !== initialProjectValue gate on the non-model
    project branch. Previously every effective/inherited project key was
    persisted as an explicit override on every save.

Git Manager UI lie in remote-only mode:
  - "Local <branch> vs origin" card now renders "no local tracking"
    instead of a green "Synced" badge when integrationTipSource ===
    "remote-only" (no local branch to compare).
  - New dedicated "HEAD vs origin/<branch>" card surfaces a meaningful
    distance in remote-only mode.

isIndexStale correctness:
  - Walks up to 16 reflog entries so multi-hop misses (A→B→C without
    sync) are detected; the prior check only consulted @{1}.
  - Gated on isOnIntegrationBranch === true so a feature-branch worktree
    whose HEAD happens to descend from <integration>@{1} no longer trips
    the FN-INDEX-DESYNC warning.

Enumeration-failed events surfaced:
  - collectRecentMergeAdvances pairs events with (taskId, newSha) when
    both are present, falls back to taskId-only for early-failure events
    (e.g. "enumeration-failed") that have neither path nor newSha. The
    diagnostic outcome now surfaces on the matching advance instead of
    being silently dropped.

aheadOfIntegration semantics no longer shift:
  - Split into three distinct fields: aheadOfIntegration (HEAD vs local),
    aheadOfIntegrationRemote (HEAD vs origin/<branch>),
    aheadOfOriginIntegration (local vs origin). Consumers no longer have
    to read integrationTipSource to know which comparison they got.

currentBranch failure no longer masks wrong-branch state:
  - Distinguish "command threw" (transient git error) from "command
    succeeded with empty stdout" (legitimate detached HEAD). New
    currentBranchDetectionFailed field lets the UI surface "branch
    detection unavailable" on a real failure.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

.changeset/git-status-review-followup.md

@@ -0,0 +1,24 @@
+---
+"@fusion/dashboard": patch
+---
+
+fix(dashboard): close 7 review findings on the extended-status hardening pass
+
+Follow-up to the prior fix commit; closes 7 more issues that an independent code review surfaced.
+
+**Settings inheritance regression (high)** — `SettingsModal.handleSave`'s non-model project branch lost the "only write if changed" gate when the prior commit added null-as-delete support. Result: every effective/inherited project key was being persisted as an explicit project override on every save, silently breaking inheritance across ~30+ keys. Restored the `value !== initialProjectValue` gate, matched against the model-lane branch's existing pattern.
+
+**Git Manager `Local <branch> vs origin` card showed misleading "Synced" in remote-only mode** — when `integrationTipSource === "remote-only"`, both `aheadOfOriginIntegration` / `behindOriginIntegration` are deliberately undefined (there's no local branch to compare), but the card's render fell through to `(ahead ?? 0) === 0 && (behind ?? 0) === 0 → "Synced"`. Now renders an explicit "no local tracking" sub-text in that case, with a separate `HEAD vs origin/<branch>` card surfacing a meaningful distance.
+
+**`isIndexStale` extended to multi-hop and gated to integration-branch worktrees** —
+- Walks up to 16 `refs/heads/<integration>` reflog entries so an A→B→C burst whose middle sync also missed is detected (the prior check only consulted `@{1}`).
+- Only fires when `isOnIntegrationBranch === true`. Previously, a feature-branch worktree whose HEAD happened to descend from `<integration>@{1}` (e.g. `git switch -c hotfix main@{N}`) would trip the stale-index warning despite being perfectly healthy.
+
+**`enumeration-failed` auto-sync events no longer dropped** — the new `(taskId, newSha)` join filter required both `worktreePath` and `newSha` on every auto-sync event, which discarded the merger's early-failure events that emit neither. Now: events with both fields use the per-advance pair-key (with macOS realpath canonicalization on both sides); events with neither use a task-id fallback so the diagnostic outcome still surfaces on the matching advance.
+
+**`aheadOfIntegration` no longer silently shifts semantics** — split into three distinct distance fields so consumers don't have to read `integrationTipSource` to know which comparison they got:
+- `aheadOfIntegration` / `behindIntegration` — HEAD vs **local** integration tip; undefined when only the remote tip exists.
+- `aheadOfIntegrationRemote` / `behindIntegrationRemote` — HEAD vs `origin/<integrationBranch>`; defined whenever the remote tracking ref exists.
+- `aheadOfOriginIntegration` / `behindOriginIntegration` — local integration tip vs `origin/<integrationBranch>`; defined only when both refs exist.
+
+**`currentBranch` failure no longer masks wrong-branch state** — `git branch --show-current` returns empty on detached HEAD (success) and throws on transient git errors (lock contention, timeout). The prior catch collapsed both into `currentBranch = ""` so the UI couldn't distinguish them. New `currentBranchDetectionFailed?: boolean` field on `GitStatus` lets the UI surface "branch detection unavailable" on a real failure rather than silently hiding the wrong-branch warning.