Structured server logging implementation plan

Goal: Make existing operational tracing events observable as structured stderr logs from every lake process.

Architecture: Subscriber ownership belongs at the binary application boundary. Domain crates continue emitting tracing events without depending on output format or deployment configuration.

Task 1: Prove the process-level logging contract

1. Add integration tests that launch the compiled binary as a subprocess.
2. Assert JSON mode emits a parseable startup record before clap rejects an invalid command and never writes logs to stdout.
3. Assert an invalid format fails before a requested data directory is created.
4. Lock the default JSON/filter behavior and pretty stderr/ANSI behavior with subprocess and captured-subscriber tests.
5. Run the tests and confirm RED because no subscriber/configuration exists.

Task 2: Install the subscriber at startup

1. Add tracing-subscriber with env-filter, fmt, and json features.
2. Parse the two environment boundaries with explicit defaults and errors.
3. Install JSON or pretty stderr output before command parsing.
4. Emit one version-only startup event and confirm both tests GREEN.

Task 3: Document and verify

1. Document defaults, environment overrides, stderr/stdout separation, and the no-sensitive-fields boundary.
2. Run spec lifecycle, strict clippy, and the full local gate.
3. Obtain independent verifier and reviewer approval, then ship and merge.