fix(sync): remediation pass on Sync tab redesign stack

[kunickiaj]

Description

Remediation PR on top of #963–#966. Addresses the findings from four
brutal reviews across the stack. Batched here so reviewers see one
coherent "Ramsay fix" diff instead of amending four in-flight PRs.

Bugs fixed

• Deep-link regression (ui(sync): carve Advanced diagnostics into #sync/diagnostics sub-view, remove Overview card #963, P0). Bookmarking `#sync/diagnostics`
  no longer lands on the main view. `setActiveTab` now only rewrites
  the hash when the top-level tab actually changed; a new
  `parseTabFromHash` helper centralizes the sub-view-aware split.
• Hashchange listener mismatch (ui(sync): carve Advanced diagnostics into #sync/diagnostics sub-view, remove Overview card #963, P0). `app.ts` now uses
  `parseTabFromHash` too, so sub-view hash transitions (e.g. back
  button from `#sync` → `#sync/diagnostics`) fire `switchTab`
  correctly.
• Dead `listMount`/`listHeading` plumbing (ui(sync): carve Advanced diagnostics into #sync/diagnostics sub-view, remove Overview card #963, P1). Removed
  from `TeamSyncPanelProps` and `render-team-sync.ts`. The old
  `listHeading = list?.previousElementSibling` was toggling the wrong
  sibling's `hidden` after the `#syncTeamStatus` element was
  removed — silent visibility corruption.
• Row `` a11y grenade (ui(sync): compact device rows with click-to-expand drawer + shared primitives #964, P0). The row head is no
  longer a ``. The chevron is now the only interactive
  element (`.device-row-toggle`), with a clean accessible name
  ("Expand device {name}"). Badges, direction glyphs, and the name
  with its `title` attribute no longer pollute the button's
  accessible-name computation.
• `ActionShelf` and `TrustChip` shipped unused (ui(sync): compact device rows with click-to-expand drawer + shared primitives #964, P2).
  Deleted both; along with their dead CSS (`.action-shelf`,
  `.settings-button.sync-btn-primary`, `.peer-scope-chip`
  tone variants). Reintroduce when a consumer actually needs them.
• `syncing` pip override is vaporware (ui(sync): syncing-pip override, device-row skeleton, empty-state rewrite #965, P1). Reverted. The
  local `syncBusy` state only fires on the per-row Sync-now button;
  global Sync now never flipped any row, and the backend has no
  per-peer in-flight signal. The pulse CSS stays so the state is
  ready when a real signal lands. Filed as follow-up.

Doc drift fixed (#966)

• Removed phantom `--pip-size-sm` / `--pip-size-md` tokens
  (PresencePip sizes are just `6 | 8` literals).
• Removed `--accent-warm-strong` implication that attention pips
  use a distinct hue — they don't, the CSS falls back to
  `--accent-warm`. Pulse alone distinguishes attention from offline.
• `DeviceRow` props block relabeled as a proposed interface; the
  real component is still `SyncPeerCard`.
• Deleted `action-shelf-anatomy.md` (no consumer primitive).
• Updated "don't nest drawers" anti-pattern to acknowledge that
  inline sub-disclosures inside a drawer are fine
  (`PeerScopeCollapsible` inside the device drawer is the example).
• Focus-management claim clarified as emergent, not designed.

Code smell sweep (#964)

• Deleted underscore-prefixed dead vars (`_effectiveInclude`,
  `_effectiveExclude`, `_inheritsGlobal`, `_summaryText`).
• Moved the mid-file `renderIntoSyncMount` import to the top.

Type of Change

• Bug fix
• Code cleanup
• Documentation correction

Testing

• `pnpm run tsc && pnpm run lint && pnpm run test` (1475 passing,
  386 files linted — 2 fewer than before thanks to the primitive
  deletions).
• Manual next step: bookmark `#sync/diagnostics`, reload, verify the
  sub-view loads; tab through the device row, verify only the chevron
  receives focus.

Stacks on #966. Closes out the Ramsay review feedback across the
redesign stack.

[kunickiaj]

• fix(sync): remediation pass on Sync tab redesign stack #967 👈 (View in Graphite)
• docs(design): Sync tab redesign handoff anatomy pages #966
• ui(sync): syncing-pip override, device-row skeleton, empty-state rewrite #965
• ui(sync): compact device rows with click-to-expand drawer + shared primitives #964
• ui(sync): carve Advanced diagnostics into #sync/diagnostics sub-view, remove Overview card #963
• main

This stack of pull requests is managed by Graphite. Learn more about stacking.

[kunickiaj]

Merge activity

• Apr 23, 11:35 PM UTC: A user started a stack merge that includes this pull request via Graphite.
• Apr 23, 11:48 PM UTC: Graphite rebased this pull request as part of a merge.
• Apr 23, 11:49 PM UTC: @kunickiaj merged this pull request with Graphite.