feat(logging): tracing diagnostics with --log-format/--log-level (#51) (#124)

Add tracing + tracing-subscriber. Global --log-format=pretty|json and
--log-level flags (precedence --log-level > RUST_LOG > info). The
subscriber writes to stderr so the stdout data contract is never
contaminated: JSON reports, the version string, the octad table, and
the status/gc/validate report bodies stay on stdout verbatim. Only
genuine diagnostics (schema parsing, file-write progress, "checking
drift", "created manifest") become tracing events. JSON log schema
documented in docs/logging.adoc + docs/logging.schema.json. New
acceptance suite tests/logging_test.rs (6 tests): stdout purity,
JSON-line schema validity, level filtering, RUST_LOG precedence.

Closes #51.

Co-authored-by: hyperpolymath <hyperpolymath@users.noreply.github.com>
Co-authored-by: Claude Opus 4.7 <noreply@anthropic.com>

Author: hyperpolymath

Cargo.toml

@@ -22,7 +22,8 @@ thiserror = "2"
 chrono = { version = "0.4", features = ["serde"] }
 sha2 = "0.10"
 rusqlite = { version = "0.32", features = ["bundled", "hooks"] }
-sqlparser = "0.50"
+tracing = "0.1"
+tracing-subscriber = { version = "0.3", features = ["env-filter", "json"] }
 
 [build-dependencies]
 chrono = "0.4"