docs(claude): slim CLAUDE.md to orientation+behavior; move niche sections to docs/ (#709)

Cuts the per-session/per-heartbeat instruction tax (CLAUDE.md is loaded into
every Claude Code session and every Paperclip agent heartbeat). 779 -> 155
lines / 40KB -> 11KB by moving reference-heavy sections into docs/ and pointing
to them, deleting auto-generated noise, and fixing a stale linter note.

## Changes
- Move to docs/development/: web-ui-verification.md (Playwright sweep),
  macos-tray.md (tray build + ui-test), server-edition-multiuser-auth.md (Spec 024)
- Compact CLI/endpoint/health/sensitive-data sections to summaries + doc links
- Delete auto-generated 'Active Technologies' (~45 lines) + 'Recent Changes'
- Fix linter guidance: CI uses golangci-lint v2 (.github/.golangci.yml), stricter
  than the local v1.x scripts/run-linter.sh
- Patch .specify/scripts/bash/update-agent-context.sh so 'Active Technologies'
  no longer regrows on every speckit run (clears new_tech_entries)
- Preserve all behavioral directives (autonomy, TDD, stop conditions) verbatim

Author: Dumbris