feat(session): artifacts panel and inline annotations

[setkyar]

Summary

Adds an in-browser review surface to the session viewer via the right sidebar (Scratchpad / Artifacts / Annotations tabs). The motivation: a long agent session produces files and decisions buried in a linear transcript — this makes the outputs easy to find, preview, and review, and lets you push structured feedback straight back to the agent.

• Artifacts panel — a path-keyed, edit-aware registry reconstructs each file's latest state from the structured tool calls (write/edit, plus a conservative mv/git mv/rm recognizer; arbitrary shell is intentionally left alone). Source view with copy/download, sandboxed HTML/SVG preview and inline Markdown preview, and a help (?) modal that explains the bash-staleness limitation in plain language.
• Artifacts settings & filter — two server-backed settings (artifacts:enabled, artifacts:include, default *.md, *.html) let users hide the Artifacts tab entirely or scope it to specific paths. Filtering is a pure frontend pass over the unchanged registry (artifact-filter.js): matching file artifacts are kept; loose chat snippets are dropped whenever a filter is active; the empty state links to Settings when artifacts are hidden. Disabling hides the tab and falls back to Scratchpad.
• Annotations — offset-anchored highlights on transcript messages and artifact source, persisted in SQLite (/api/annotations, GET/POST/DELETE) and synced across tabs via an annotations SSE snapshot. Mobile-friendly selection → note-modal flow (selectionchange trigger for touch). "Send notes to pi" groups notes by file with line numbers and fills the composer with a directive framing.
• Backend/infra — new annotations table + handlers; SQLite pool capped to one connection (SetMaxOpenConns(1)) so concurrent writers queue instead of hitting "database is locked".
• Docs — new artifacts.md / annotations.md sequence-flow deep-dives (artifacts.md now covers the filtering model); architecture docs and AGENTS.md updated for the new endpoint, SSE event, and frontend modules.

Related issue

Closes #

Type of change

• feat — new feature
• fix — bug fix
• docs — documentation only
• refactor — code change that neither fixes a bug nor adds a feature
• style — formatting / UI styling, no behavior change
• test — adding or updating tests
• chore — build, tooling, or maintenance

Live vs. Export

• Considered both the live app and the export snapshot
• Kept internal/ui/live_templates/ in sync with web/src/session/ changes
• No live-only chrome (Vite scripts, active composer, SSE/API) leaked into export — the artifacts/annotations hosts render only when IsLive, so the layers are no-ops in exported Gist snapshots

Testing

• make check passes (test + build + vet)
• Frontend tests (vitest) cover the change — registry/panel/filter, annotation range/api/layer, tab controller (445 tests)
• Go tests (go test ./...) cover the change — annotations_test.go (create/list/upsert/delete/validation/scoping)
• UI changes verified in a browser — Playwright E2E (artifacts.spec.ts incl. include-filter / empty-state / disabled-tab cases, annotations.spec.ts) across desktop, mobile, and iPad projects

[setkyar]

Annotation panel UX: reveal on save + mobile send

Two follow-up commits improving how the right sidebar behaves around annotations:

2b6dd4f — reveal the panel on the Annotations tab when a note is saved

• Saving a note now fires an onCreate callback that opens the right sidebar if it's collapsed and switches to the Annotations tab, so the just-created note is always visible where it lands.
• New open-only openSidebar() on the right-sidebar controller (won't toggle an already-open panel shut).

6ca883a — collapse the sidebar and focus the composer on mobile send

• On mobile the right sidebar is a full-screen overlay, so "Send N notes to pi" now fires an onSend callback that collapses the sidebar (mobile only, max-width: 900px) before the just-filled composer is focused — leaving it visible and ready to type into. Desktop keeps the sidebar in place.
• New collapseSidebar() on the controller.

Tests

• Unit (annotation-layer.test.js): onCreate fires on save; onSend fires once and runs before focus.
• E2E (annotations.spec.ts): reveal-on-save (starts collapsed, asserts it opens on the Notes tab); layout-aware mobile-send test (mobile projects assert collapse + composer focused; desktop/iPad-landscape assert the sidebar stays put). All 35 annotation E2E cases pass across 7 browser projects.
• make check green; docs updated in docs/sequence-flows/annotations.md.