fix(671): make session-less control events (server_start) readable by harness + AI

[jonathaneoliver]

Completes #671 part 1's visibility goal. The server_start boot marker (#672) was archived in ClickHouse with the right label, but unreadable through any operator/AI path — verified live: GET /api/v2/control_events?event=server_start returned 400 player_id required.

Two root causes, both fixed:

1. The read path hard-required player_id, but server_start is deliberately session-less.
2. The handler never read an event filter at all — so harness query control --event … was a silent no-op (the generated client sent it; the server ignored it).

Plumbed across all four read layers

A query now needs ≥1 discriminating predicate (player_id | play_id | event | label_has) so it can never scan the whole table — but player_id is no longer mandatory.

• internal/plays/control.go — ControlEventsFilter gains Events []string; the player_id-required hard error becomes the discriminator guard (shared by AI + HTTP).
• v2_handlers.go — reads repeatable ?event=, player_id optional, same guard.
• llm_tools_tier1.go — get_control_events gains an event arg, drops required:[player_id]; description tells the AI it can query server_start (and other global events) by event name with no player_id.
• tools/harness-cli/.../query.go — the positional play_id is now optional; omit it and pass --event/--label-has to query global events.
• .claude/standards/data-fields.md — corrected the server_start query examples to the now-working forms (harness query control --event server_start); the old --label-has-on-plays example couldn't surface a play-less event.

Now works

harness query control --event server_start
GET /api/v2/control_events?event=server_start
get_control_events(event="server_start")   # AI tool, no player_id

Tests

Guard rejection unit-tested (internal/plays/control_test.go). Forwarder + plays suites pass; harness-cli builds; go vet + gofmt clean. Positive path will be verified live post-deploy (query the server_start rows that already exist on test-dev).

🤖 Generated with Claude Code