feat(cicontext): rules:changes: path-glob evaluation; 100% test coverage

- Add --changes PATH and --changes-from REF flags to glint check and glint graph
  for rules:changes: evaluation. --changes marks files explicitly; --changes-from
  runs git diff --name-only <REF> automatically. Both flags can be combined.
- Implement doublestar glob matching (*, ** across path segments) in EvalJob and
  EvalWorkflow; extended {paths, compare_to} map form supported.
- Without --changes/--changes-from the condition stays permissive (existing behaviour).
- Context summary line now shows changed-file count when file data is provided.
- Achieve 100% statement coverage: comprehensive tests added across all packages;
  removed provably dead code; added testability seams (exit, userHomeDirFn,
  execCommandOutput variables) to cover previously unreachable paths.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

CHANGELOG.md

@@ -5,17 +5,26 @@ All notable changes to this project will be documented in this file.
 The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.1.0/).
 This project uses [Semantic Versioning](https://semver.org).
 
-## [0.2.21] - 2026-06-14
+## [0.2.21] - 2026-06-21
+
+### Added
+
+- **`rules:changes:` evaluation** — `glint check` and `glint graph` now evaluate `rules:changes:` conditions when file-change data is provided. Two new flags on both subcommands:
+  - `--changes <PATH>` — mark one or more file paths as changed (repeatable).
+  - `--changes-from <REF>` — run `git diff --name-only <REF>` to determine changed files automatically (e.g. `--changes-from origin/main`).
+  Both flags can be combined. Glob patterns in `rules:changes:` support `*` (within a path segment) and `**` (across segments). When neither flag is given the condition is treated as always matching (permissive), preserving the existing behaviour. The extended map form `{ paths: [...], compare_to: ... }` is also supported.
+
+- **`workflow:rules:changes:` evaluation** — `workflow:rules:` entries now also evaluate `changes:` patterns when changed-file data is available, consistent with job rules.
+
+- **Context summary includes changed files** — the `Context:` line printed by `glint check --format text` now shows the count of changed files when `--changes`/`--changes-from` is given (e.g. `branch=main, source=push, 3 changed file(s)`).
+
+- **Unit test suite** — 100% statement coverage across all packages (`cmd/glint`, `internal/cicontext`, `internal/fetcher`, `internal/graph`, `internal/linter`, `internal/model`, `internal/resolver`).
 
 ### Changed
 
 - **Internal:** replaced all `os.Exit` calls in `cmd/glint` with an `exit` variable to enable unit testing without process termination; no behaviour change.
 - **Internal:** removed unreachable code paths found during coverage analysis — dead guard in `cicontext.parseRegexLiteral`, unreachable `len(jobs) == 0` branch in `graph.Pipeline`, and the `skipWin` struct field / dead `continue` in `graph.convertToPNG`; `pipelineSVG` return type simplified from `(string, error)` to `string` as it never returned a non-nil error. No behaviour change.
 
-### Added
-
-- **Unit test suite** — comprehensive table-driven tests added across all packages (`cmd/glint`, `internal/cicontext`, `internal/fetcher`, `internal/graph`, `internal/linter`, `internal/model`, `internal/resolver`), reaching 98%+ statement coverage.
-
 ## [0.2.20] - 2026-06-14
 
 ### Added