Merge #97: Add comprehensive coverage documentation

f895f01 docs: [#89] add 'undertested' to project dictionary (copilot-swe-agent[bot])
bda86a1 docs: [#89] add comprehensive coverage documentation (copilot-swe-agent[bot])
4a2022e Initial plan (copilot-swe-agent[bot])

Pull request description:

  Creates `docs/contributing/testing/coverage.md` documenting code coverage practices, tooling, and expectations per issue #89.

  ## Coverage Strategy

  - **Targets**: 85% overall, 90% business logic, 95% utilities
  - **Exclusions**: Binaries, E2E infrastructure, adapters requiring real infrastructure, linting package
  - **Philosophy**: Coverage as informational tool, not blocking gate

  ## Cargo Aliases Reference

  Documents all coverage commands from `.cargo/config.toml`:

  | Alias | Purpose |
  |-------|---------|
  | `cargo cov` | Terminal summary |
  | `cargo cov-check` | Validate ≥85% threshold |
  | `cargo cov-lcov` | LCOV format (`.coverage/lcov.info`) |
  | `cargo cov-codecov` | Codecov JSON (`.coverage/codecov.json`) |
  | `cargo cov-html` | HTML report (`target/llvm-cov/html/`) |

  ## Integration Points

  - **Pre-commit**: Final step in `scripts/pre-commit.sh`, non-blocking, informational only
  - **CI/CD**: `.github/workflows/coverage.yml` generates artifacts on all pushes/PRs, non-blocking
  - **PR Reviews**: Guidelines for when to request tests vs. accepting coverage gaps

  ## Changes

  - `docs/contributing/testing/coverage.md` - New 557-line comprehensive guide
  - `docs/contributing/testing/README.md` - Add navigation link
  - `project-words.txt` - Add "undertested" term

  <!-- START COPILOT CODING AGENT SUFFIX -->

  <details>

  <summary>Original prompt</summary>

  >
  > ----
  >
  > *This section details on the original issue you should resolve*
  >
  > <issue_title>Write coverage documentation</issue_title>
  > <issue_description>**Parent Epic**: #85
  > **Prerequisites**: #88 must be completed first (testing documentation refactoring)
  >
  > ## Overview
  >
  > Create comprehensive code coverage documentation (`docs/contributing/testing/coverage.md`) to provide guidance on coverage expectations, how to run coverage locally, how coverage is checked in CI/CD, and how coverage should be evaluated in PR reviews.
  >
  > This is a **new documentation file** that will be added to the refactored testing documentation structure created in issue #88.
  >
  > ## Goals
  >
  > - [ ] Create new documentation file `docs/contributing/testing/coverage.md`
  > - [ ] Document all coverage commands and aliases
  > - [ ] Explain coverage expectations and thresholds
  > - [ ] Provide guidance for PR reviews involving coverage changes
  > - [ ] Document the pre-commit coverage check behavior
  > - [ ] Explain CI/CD coverage workflow
  > - [ ] Add link to `coverage.md` in testing README navigation
  >
  > ## Document Structure
  >
  > The new file should include these sections:
  >
  > 1. **Overview** - What coverage is and why it matters
  > 2. **Running Coverage Locally** - All cargo coverage commands
  > 3. **Coverage Thresholds** - Project targets (85% overall, granular targets)
  > 4. **What Gets Measured** - Include/exclude rules
  > 5. **Pre-commit Integration** - How coverage check runs
  > 6. **CI/CD Coverage Workflow** - GitHub Actions workflow details
  > 7. **Interpreting Results** - How to read coverage reports
  > 8. **PR Review Guidelines** - When coverage drops are acceptable
  >
  > ## Implementation Plan
  >
  > ### Phase 1: Create Core Documentation (40 minutes)
  > - [ ] Create `docs/contributing/testing/coverage.md`
  > - [ ] Write Overview and Running Coverage Locally sections
  > - [ ] Document all cargo aliases from `.cargo/config.toml`
  >
  > ### Phase 2: Coverage Strategy (30 minutes)
  > - [ ] Document coverage thresholds and targets
  > - [ ] Explain what code is measured and what's excluded
  > - [ ] Add examples of coverage output
  >
  > ### Phase 3: Integration Documentation (20 minutes)
  > - [ ] Document pre-commit coverage check
  > - [ ] Document CI/CD workflow behavior
  > - [ ] Explain non-blocking nature
  >
  > ### Phase 4: Guidance and Best Practices (30 minutes)
  > - [ ] Write section on interpreting coverage results
  > - [ ] Document PR review guidelines
  > - [ ] Add troubleshooting tips
  >
  > ### Phase 5: Navigation and Cross-linking (15 minutes)
  > - [ ] Add link to `coverage.md` in `docs/contributing/testing/README.md`
  > - [ ] Add cross-references to related documentation
  > - [ ] Verify all links work
  >
  > ### Phase 6: Review and Polish (15 minutes)
  > - [ ] Run markdown linter
  > - [ ] Review for clarity and completeness
  > - [ ] Ensure examples are accurate
  >
  > ## Acceptance Criteria
  >
  > - [ ] New file `docs/contributing/testing/coverage.md` created with complete documentation
  > - [ ] Link to `coverage.md` added in `docs/contributing/testing/README.md` navigation section
  > - [ ] All cargo coverage aliases documented (`cov`, `cov-check`, `cov-lcov`, `cov-codecov`, `cov-html`)
  > - [ ] Coverage targets clearly defined (85% overall, 90% business logic, 95% utilities)
  > - [ ] Exclusions documented (binaries, E2E infrastructure, adapters, linting tools)
  > - [ ] Pre-commit coverage check behavior is clearly explained
  > - [ ] CI/CD coverage workflow is documented
  > - [ ] PR review guidelines for coverage changes are clear
  > - [ ] All markdown passes linting
  > - [ ] All cross-references work correctly
  >
  > ## Related Documentation
  >
  > - [Testing Conventions](../testing/README.md) - Main testing documentation (after #88 completes)
  > - [Development Principles](../../development-principles.md) - Quality standards
  > - [Pre-commit Process](./commit-process.md) - Pre-commit workflow
  >
  > ## Notes
  >
  > - This is a **new file** - `docs/contributing/testing/coverage.md` does not exist yet
  > - Must be created AFTER issue #88 completes (testing documentation refactoring)
  > - The documentation should reflect actual behavior, not aspirational features
  > - Emphasize the non-blocking, informational nature of coverage checks
  > - Make it clear that coverage is a tool, not a goal
  > - Provide practical examples that contributors can run immediately
  >
  > ## Dependencies
  >
  > **Before This Issue**: #88 - Creates the `docs/contributing/testing/` directory structure
  > **After This Issue**: None - This is the final documentation task in the EPIC</issue_description>
  >
  > ## Comments on the Issue (you are @copilot in this section)
  >
  > <comments>
  > </comments>
  >

  </details>

  - Fixes #89

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ACKs for top commit:
  josecelano:
    ACK f895f01

Tree-SHA512: ef19ecbd1dbd4895cc7687a0e89b79e69b3242577f2bf0c2de789ce219015bf9ad4e53bcc7276f2b8d76225661e5a55caf78b66eccb961ab6af5ff7c682ae5e0

Author: josecelano

docs/contributing/testing/README.md

@@ -174,6 +174,7 @@ This section provides links to specialized testing documentation organized by to
 - **[Testing Commands](./testing-commands.md)** - Command test patterns, builders, mocks, E2E
 - **[Clock Service](./clock-service.md)** - MockClock usage for deterministic time tests
 - **[Pre-commit Integration](./pre-commit-integration.md)** - AI enforcement tests, SKIP_AI_ENFORCEMENT flag
+- **[Coverage](./coverage.md)** - Code coverage targets, tools, CI/CD workflow, and PR guidelines
 
 ## 🔗 Related Documentation