feat(dashboard): inbox density + keyboard cockpit + default-submit-recommended

[OriginalGary]

Stacks on #9 (cockpit chrome). Three changes that turn the Inbox from a form into a cockpit.

Density

• Compact two-line gate rows: title on row 1, slug + color-coded risk pill + playbook on row 2.
• Risk pill is now color-coded — green low, amber medium, red high, saturated red irreversible. Text-only risk: medium was invisible at scan.
• Priority rail on the left of each row (red/amber/muted by P0..P3).
• 12 gate cards above the fold on 1440×900, vs 5 originally / 9 with chrome change.
• Sort is P0-first then newest, so the keyboard 'top of list' is always the most critical gate.

Keyboard cockpit

Key	Action
j / ↓	Next gate
k / ↑	Previous gate
1–9	Pick option N
Enter	Submit selected option
⌘↵ / Ctrl↵	Submit (works inside form fields)
?	Toggle help overlay
Esc	Close help / drawer

Form fields (input / textarea / contenteditable) opt out of the letter shortcuts so typing isn't hijacked. Cmd+Enter still works inside form fields because the modifier is unambiguous.

Default-submit-recommended

When the gate carries a recommended option, the decide block is a single primary button labelled with that option ("Click merge on PR #20 — ships Wave 0 bootstrap…"), plus a change… affordance that expands the full radio group. One click + Enter ships the recommended path — the click count for the ~99% case drops from 2 (radio + submit) to 1.

The radio fieldset only opens for explicit overrides. Each option is numbered (1, 2, …) so the keyboard mapping matches what's on screen.

Test plan

• OPERATOR_BUILD=true npm run dev. /approvals=200.
• Help overlay opens on ?, closes on Esc / backdrop click. Confirmed via Playwright.
• j advances selection (URL hash flipped from 109-animal-impact-intelligence-scraper to 50-enforce-worktree-discipline).
• Enter submits the recommended option.
• 1/2 pick option 1/2.
• Risk pills render green / amber / red / saturated red for the four risk levels.
• Form fields don't intercept j/k/digits.

What's NOT in this PR

• New-since-last-visit indicator (P1 feat(api): Gary header contract — read-only parsing of X-Gary-* headers #3) — next.
• Calibration polish (target line, n>=30 gating, WoW delta).
• Activity grouping by day.