feat: reins groups — list tab groups

[karngyan]

What

People asked for a way to see which tabs reins controls. Chromium tab groups are the natural marker, and they're also a general "organize my tabs" tool. This PR is the read side. reins ships primitives only and never groups anything on its own; the agent decides.

reins groups
#   b1  group 1055697787  "Mercor"  grey  9 tabs  window 1427084784
reins tabs
#   b1  tab 1427084886    g1055697787  Title — url

• Protocol:
  • Tab.groupId (optional; left out when a tab is ungrouped).
  • A new TabGroup / ListGroupsResult.
  • list_groups at tier read.
  • On output, color is a plain string, so a future Chromium color can't reject a whole list. Inputs (next PR) use the nine-color enum.
• Extension:
  • A new tab-groups.ts.
  • groupsSupported() checks for the exact APIs used (tabGroups.query/update, tabs.group/ungroup) rather than guessing from the browser name.
  • A browser without the API gets error code unsupported. The daemon rewrites it to name the browser: <browser> (b2) doesn't support tab groups — reins groups/group/ungroup need the chrome.tabGroups API, which this browser doesn't provide. Other reins commands work normally. An older extension that doesn't know these methods gets <browser> (b2)'s reins extension predates tab groups — update it ….
  • list_groups has no host check, since group titles are the user's own labels. Denied tabs in reins tabs stay redacted and drop their groupId.
• Permission: adds tabGroups. It shows no install warning, so existing users aren't asked to re-approve on update, and browsers that don't know it ignore it.
• Daemon:
  • list_groups fans out across browsers like list_tabs, tagging each group with browserId.
  • A browser that can't answer (unsupported, older extension, or another error) is listed in skipped ({browserId, browser, reason, message}), and the text output prints a line such as b2 <browser> — tab groups not supported. Nothing is dropped silently.
  • It only errors when every browser fails.
• Docs: SKILL.md, the web commands page, Chrome Web Store permission justification, privacy policy, and a minor changeset. The store copy already covers the write side (feat: reins group / ungroup — create, edit and dissolve tab groups #35, stacked on this), because both land in the same release.

Spec and plan are in docs/superpowers/.

Test plan

• pnpm build && pnpm test && pnpm typecheck && pnpm lint: all green.
• Unit tests:
  • Capability detection (missing tabGroups, missing tabs.group).
  • unsupported code and message.
  • Tab counts per group.
  • groupId mapping (-1 left out).
  • list_groups bypasses the host gate.
  • Redaction drops groupId.
  • Daemon aggregation: all ok, partial failure, total failure, no browsers, unknown browserId.
  • Text output.
• Live in Chrome (sideloaded build, reins extension --reload): reins groups listed an existing group correctly, and reins tabs marked its tabs. Read-only, nothing mutated.
• Live in Dia alongside Chrome: Dia supports tab groups (it connects as "Chromium"). reins groups lists both browsers' groups, with skipped: [].
• Unit tests for the named errors and skipped browsers: partial failure, total failure, outdated extension, generic error, routed group call with the audit record, non-group methods untouched, and text output.
• Not live-tested: a browser that actually lacks tab groups, since none is available here. Unit tests only.

Stacked PR with reins group / reins ungroup: #35.

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