Add privacy-safe CLI and TUI recordings

[tony]

Summary

• Keep the synthetic recording corpus, recorder inputs, rendered media, and still posters together under docs/_static/demos/.
• Record 16 VHS scenarios across root help, search, grep, find, JSON/NDJSON, and two TUI workflows, plus canonical asciinema casts for search, grep, find, and ui.
• Add a local-only {terminal-demo} directive that derives intrinsic geometry from an explicit poster and emits a native, no-JavaScript MP4 player with accessible builder fallbacks.
• Embed six primary CLI and TUI recordings in their reference pages, while the README keeps linked posters with explicit dimensions.
• Publish the 16 MP4 recordings and six posters through Sphinx while keeping casts, tapes, helpers, GIFs, and WebMs out of the static copy.
• Keep the recording and documentation work in ten reviewable commits, with the pnpm regression fix in one separate CI commit.

Color and safety

• Seed only synthetic Codex, Claude, Cursor, and Gemini history, and neutralize every catalogued store override plus the WSL host probe before agentgrep starts.
• Reject seeding outside the fixed synthetic sandbox before cleanup.
• Remove ambient NO_COLOR and FORCE_COLOR at the recording boundary and set truecolor explicitly. The old environment made Textual install its no-color filter, which stripped the TUI palette and materialized terminal-default backgrounds as black.
• Scan sources, casts, captures, and metadata for developer paths, emails, credentials, secrets, and non-synthetic prompt content.

Preview

CLI

TUI

Verification

• rm -rf docs/_build; uv run ruff check . --fix --show-fixes; uv run ruff format .; uv run ty check; uv run py.test --reruns 0 -vvv; just build-docs;
• 2,301 tests passed, 3 skipped, and 3 strict xfails remained expected; 2 snapshots passed.
• Both TUI capture families decode at 1200 by 700 across GIF, MP4, and WebM; their populated posters decode at the same geometry.
• The built site contains native players for all six referenced demos, with typed MP4 sources, intrinsic dimensions, controls, and preload="none".
• The built site contains all 16 MP4s and six posters under _static/demos/, with no recorder sources or alternate media in the static demo copy.
• Focused directive tests cover asset confinement, required alt/poster metadata, playback sources, copied files, and non-HTML fallbacks.
• The final pull-request docs and test jobs passed after removing the temporary preview deployment; normal master-only publication rules are restored.