docs: add CLI reference and RunEvent field table

[cursor]

Docs added/updated

New: docs/cli.md — CLI reference

Adds a complete CLI command reference covering every flightdeck command as a stable public contract (v1.0.0+):

• Global flags and exit code table (0 = success, 1 = error, 2 = checksum mismatch)
• flightdeck init, doctor, serve with all options
• release subgroup: register, list, show, verify, diff, promote, rollback, history
• pricing subgroup: import (including --replace/--reason semantics) and show
• policy subgroup: set and show
• runs subgroup: ingest (JSONL and JSON array formats)
• End-to-end typical workflow walkthrough

Updated: docs/http-api.md — RunEvent field reference

Adds a RunEvent field reference table to the POST /v1/events section covering:

• All top-level fields with types, required/optional, defaults, and descriptions
• metrics sub-object fields (success, latency_ms, error_type)
• usage.model fields (all token count fields and provider/model)
• usage.tools[] entry fields

Updated: README.md

Links the new docs/cli.md in the Documentation section and notes the RunEvent field reference in the HTTP API entry.

Which codepaths they cover

• src/flightdeck/cli/main.py — all CLI commands, flags, exit codes
• src/flightdeck/models.py — RunEvent, RunEventMetrics, RunEventModelUsage, RunEventToolUsage
• src/flightdeck/server/routes/ingest.py — event validation and api_version handling
• src/flightdeck/storage.py — insert_run_events idempotency (duplicate run_id handling)

Key knowledge gaps addressed

1. No CLI reference existed — developers had to run --help for each subcommand to discover flags and exit codes. The release verify exit-2 contract and the pricing import --replace audit requirement were especially non-obvious.
2. RunEvent structure was undocumented — the HTTP API docs showed an example JSON body but gave no per-field semantics for type, metrics.*, usage.tools[], or which fields are required vs optional. This is the primary input format for runtime evidence ingestion.