Activity tab + Bolts intent picker

[dnapoleon]

Take it or leave it. I needed a more organized way to see it.

Summary

• New Activity tab split out of the Bolts tab as a peer (Activity → Bolts → Specs → Overview). Fills the whole pane; resize handle and persisted height removed.
• Intent picker on the Bolts tab replaces the static "Current/Next Intent" display. Dropdown lists every intent in the workspace; backend-active intent marked (current). Selection is in-session, not persisted across reloads.
• Per-intent progress bar — percent complete and breakdown (in-progress / queued / blocked) now reflect only the selected intent. Backend computes stats from the full bolt arrays so older completions still count.
• Filtered Up Next — only queued/blocked bolts for the selected intent.
• Filtered Completions (now titled "Completions") — only completions for the selected intent. Removed the global 10-completion cap so per-intent lists are accurate. Globally-recent completions remain available via the Activity tab.
• Styling tweaks — smaller picker font (12px / 600), inner container with 4px breathing room around the picker + progress block, removed the orange top border on the Bolts tab for consistency with sibling tabs.

Backend plumbing

• QueuedBoltData, ActiveBoltData, CompletedBoltData each gained intent, intentNumber, intentName fields, resolved by matching the bolt's raw intent string against state.intents by number, name, combined \${number}-\${name}, and folder basename (covers full-folder-name conventions like 007-platform-tenant-access).
• boltsData postMessage payload now includes boltIntents: { number, name }[] and intentStats: Record<string, BoltStats>.
• Webview app.ts splits the legacy activity fields off the incoming bolts payload into dedicated state used by the Activity tab.

Test plan

• `npm run compile` clean (extension + webview)
• `npm test` — all 412 tests pass
• F5 the extension against a real workspace and confirm:
  • Tab order is Activity, Bolts, Specs, Overview
  • Activity tab fills the pane; filter + open-file still work
  • Bolts tab has the intent dropdown; current intent is marked (current)
  • Switching intents updates the progress bar, Up Next, and Completions consistently
  • Intents with only old completed bolts (pushed past the previous 10-cap) now show accurate progress

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