v2.0.0: SQLite, generic events, triage skill

Breaking operational contract, compatible API.

• Storage: PostgreSQL replaced by SQLite (modernc.org/sqlite, pure Go).
  One container, one named volume, no database service. Physical backups via
  feedback backup, logical via GET /api/v1/export; restore and migration
  via feedback import (all-or-nothing, header/count/digest verified, hashes
  recomputed, --family filter, ids never reused). See
  operate.md
  for the 1.x migration procedure; scripts/export-v1-postgres.sh produces
  the import file from a 1.x deployment with ids, timestamps, processing state
  and hashes preserved.
• API 1.1 (api.md): additive. family and payload_hash on
  every record, POST /api/v1/events, resolution when marking processed,
  keyset pagination (before_id, has_more, next_before_id, total),
  include=payload, GET /api/v1/export, six-digit timestamps. Every 1.0
  request and response field is unchanged.
• Service: stdlib net/http, Prometheus with bounded labels plus backlog,
  database size and busy counters. OpenTelemetry, chi, sqlc and the
  PostgreSQL-specific configuration are gone. GRACEFUL_SHUTDOWN_TIMEOUT
  default is now 30s; the fixed 5s drain sleep is removed. Payloads are
  returned byte-exact (large integers no longer round).
• Deployment: scripts/deploy.sh <sha> installs the compose file,
  preserves the host .env, pins the image there and runs docker compose pull && up. Requires the GHCR package to be pullable by the host. The
  crane streaming path is gone.
• Skill agent-feedback 3.0: new submit-event.sh; process.sh list
  pages through the whole queue and takes --include-processed (the old
  --all errors), done takes --resolution; query.sh export;
  submit-review.sh --sweep scans REVIEW_LOG_DIR and
  AGENT_FEEDBACK_REVIEW_DIRS only (set the latter where hardcoded cache
  paths were relied on). Fixes: spool persistence is verified (an unwritable
  spool now fails loudly instead of reporting spooled), review receipts are
  validated before a run is marked submitted, large prose no longer passes
  through argv, --dry-run applies the server's validation, rejected spool
  files are kept 30 days as documented.
• New skill feedback-triage 1.0: end-to-end queue processing with one
  consolidated interview. scripts/digest.sh pulls and groups the open queue.
• Docs rewritten for agents first: README route table, api.md,
  operate.md, develop.md, security.md. Template-era documents removed;
  docs/agent-usage.md redirects to api.md.

Upgrade: follow the migration procedure; the 1.x PostgreSQL volume is not
read by 2.x. Producers need skill 3.0 only for the new features; 2.1 clients
keep working against the 2.0.0 service.