Dashboard Cockpit layout, RESEARCH/REVIEW tool-access fix, Quick Create mode picker

[Codename-11]

Summary

Three independent pieces from one session:

• Dashboard: Cockpit layout. Replaces the single stacked column with a
  two-column cockpit — a wide primary work column (Focus today, Pick up where
  you left off, a new Pipeline bars card, Suggestions) beside an
  always-visible rail (the existing customizable widget stack, now forced to
  one column). Chosen after mocking up 3 layout directions (Cockpit / Bento /
  Priority-bands) to address reported "too much scrolling / empty gaps /
  doesn't flow" complaints. DashboardStack gains a columns?: 1 | 2 prop
  (default 2, back-compat — it's only used on this one page).
• Fix: RESEARCH/REVIEW tool access. runtimeModeToolCapabilities() was
  returning zero host tools for any non-EXECUTE mode with no explicit
  modeToolProfiles override — contradicting
  docs/agents/engagement-modes.md's own promise ("Research: read, search,
  run read-only tools"). Now defaults RESEARCH/REVIEW to the read-oriented
  subset (filesystem, git — never terminal) of whatever the runtime
  declared. (Separately: web-search availability is not a Forge concept at
  all by design — that's a Hermes-gateway-config question, out of scope here.)
• Quick Create: engagement mode picker on /assign. The new-issue overlay
  could assign an agent but had no way to set the run's engagement mode — the
  server hardcoded explicit: null. Added an optional mode to the assign
  slash command (UI-only) and a compact 4-button picker next to the assign
  badge, reusing the same glyph/order as the issue-detail AgentPickerModal.
  No schema change needed.

Verification

• pnpm typecheck && pnpm lint && pnpm build — all clean.
• New tests/unit/runtime-tools.test.ts (7 cases) + existing
  slash-commands.test.ts / chat-slash-command-gating.test.ts — 36/36 pass.
• Both UI-facing changes verified end-to-end against dev:local with real
  seeded data via scripted Playwright (login → dashboard render with 3-col
  Focus grid + populated rail; quick-create /assign victor → mode picker
  appears unselected → click Research → aria-checked flips correctly).
• Pre-existing, unrelated: this worktree's node_modules is missing the
  server-only package, failing 21 tests/unit/*.test.ts files that don't
  touch any file in this diff (confirmed via ls node_modules/server-only
  vs. the main checkout, and pnpm install didn't resolve it) — an
  environmental gap, not a regression from this change.

Test plan

• Open the workspace dashboard — confirm the two-column cockpit layout,
  Pipeline card, and rail render correctly with real data.
• Assign an agent to a Research-mode dispatch on a Hermes runtime with no
  modeToolProfiles override — confirm it now gets filesystem/git tools.
• Open Quick Create (C), type /assign @<agent>, confirm the mode
  picker appears and persists the chosen mode onto the created issue's run.

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