docs(lethe-web-ui-aggregates): add implementation plan

docs: add roadmap TODO and lethe-web-ui-aggregates design

TODO.md indexes all 9 task specs (4 done/in-progress, 5 deferred or
blocked) plus the carry-overs from the foundation Conclusion. New task
file lethe-web-ui-aggregates covers the backend /projects + /stats
endpoints and the three frontend screens (Projects index, Project
detail, Stats), replacing three of the foundation's stub routes.

docs(lethe-web-ui-foundation): record review conclusion, mark Reviewed

Two Important findings from the independent review pass were resolved:
keyboard g-leader / palette-input interference (4ef7a02), and Dockerfile
web-builder path fragility plus uncovered Go-1.26 requirement (0cf348a).
Future work captured: composite-id URL, aggregates absent on Get, Turn
meta-line timestamp, stray flatted/ Go package. CI config remains
deferred pending user choice between .github/ and .sourcecraft/.

docs(lethe-web-ui-foundation): record verify section, mark Verified

End-to-end browser smoke confirmed shell, Home (with real ingested data
showing all aggregate columns), Session view (markdown rendering, role
glyphs, breadcrumb), ⌘K palette, tab navigation. Three minor follow-ups
captured in Notes (composite-id URL encoding, zero aggregates on Get
path, stray flatted Go package in npm dep).

docs(lethe-web-ui-foundation): record execute deviations across all 6 phases

All six phases implemented, signed, and tested green. Backend aggregates
(Phase 1) ship a strict superset of the prior /api/v1/sessions response.
Web SPA (Phases 2-6) is embedded into the Go binary; vite dev mode
proxies the API with a Remote-User header injection so forward-auth
passes without a real reverse proxy. Status flipped to "Execute (verify
pending)" pending up:uverify.

docs(lethe-web-ui-foundation): import design handoff, add task file

Bring in the React prototype bundle from the claude-design handoff
(`docs/design_handoff_assistant_log/`) and the new task file
(`docs/tasks/lethe-web-ui-foundation.md`) covering the foundation slice
of the assistant-log web UI: scaffold, embed pipeline, shell, Home, and
Session view. Backend additions to `/api/v1/sessions` (summary,
turn_count, token totals, model) are part of this task; Projects, Stats,
Search, Health, and Settings are split into deferred sibling tasks.

docs(lethe-server): record verify section, mark Verified

docs(task): record execution conclusion across all 9 phases

feat(http): chi server with middleware stack + RFC 7807 problem renderer

feat: bootstrap lethe server skeleton + wire contract

docs: add lethe task specs (server, collector, search)