091: Raise per-crate coverage gate to 90%

• Status: Accepted
• Date: 2026-01-17
• Context:
  • The workspace coverage gate previously enforced ≥80% line coverage overall, which masked low-coverage crates.
  • The requirement is now ≥90% coverage per crate, without test-only code in production modules.
  • The gate must remain Justfile-driven and avoid llvm-cov suppression flags.
• Decision:
  • Update just cov to run cargo llvm-cov per crate and enforce a ≥90% threshold via the Justfile loop.
  • Raise the documented coverage requirement in AGENT.md to 90% per crate.
  • Add focused unit tests to raise coverage in low-coverage crates (test-support, asset_sync, doc-indexer, CLI, API setup/docs, UI ANSI parsing, libtorrent types).
• Consequences:
  • Coverage checks now report per-crate deficits with precise percentages.
  • The stricter gate currently fails on multiple crates until additional tests are added.
  • More test investment is required for large modules (API handlers, config loader, fsops pipeline, app bootstrap).
• Follow-up:
  • Add tests to raise coverage for: revaer-app, revaer-config, revaer-data, revaer-fsops, revaer-api, revaer-ui, revaer-torrent-libt, asset_sync, and revaer-test-support.
  • Re-run just cov, then complete the full just ci and just ui-e2e gates.

Motivation

• Ensure test coverage reflects real production risk by enforcing ≥90% per crate.

Design notes

• Coverage is computed per crate by running cargo llvm-cov --package in a workspace member loop.
• Crates with zero executable lines are treated as 100% covered by llvm-cov for that package.

Test coverage summary

• just cov run on 2026-01-17; coverage gate failed. Current per-crate results:
  • revaer-app: 70.71% (1922/2718)
  • revaer-test-support: 71.30% (246/345)
  • revaer-data: 72.75% (993/1365)
  • revaer-config: 75.65% (2775/3668)
  • revaer-fsops: 76.15% (1520/1996)
  • asset_sync: 79.16% (300/379)
  • revaer-ui: 83.82% (1911/2280)
  • revaer-api: 84.37% (7539/8936)
  • revaer-torrent-libt: 85.38% (2961/3468)
  • revaer-cli: 86.51% (2084/2409)
  • revaer-doc-indexer: 89.73% (655/730)
  • revaer-telemetry: 92.40% (729/789)
  • revaer-torrent-core: 94.34% (250/265)
  • revaer-api-models: 95.34% (553/580)
  • revaer-events: 96.40% (268/278)
  • revaer-runtime: 100.00% (0/0)

Observability updates

• None.

Risk & rollback plan

• Risk: CI remains blocked until per-crate coverage is lifted to 90%.
• Rollback: revert the just cov loop and reset the coverage threshold (not recommended unless blocking critical releases).

Dependency rationale

• No new dependencies added.