chore: remove dead functions (phase 6) — parser frontmatter

[dsyme]

Remove 5 unreachable functions:

• ExtractFrontmatterString (frontmatter_content.go)
• ExtractYamlChunk (frontmatter_content.go)
• ComputeFrontmatterHash (frontmatter_hash.go)
• buildCanonicalFrontmatter (frontmatter_hash.go)
• ComputeFrontmatterHashWithExpressions (frontmatter_hash.go)

Part of dead code cleanup — see DEADCODE.md

[Copilot]

Pull request overview

Removes dead/unreachable frontmatter parsing and hashing helpers as part of the ongoing dead code cleanup (phase 6), and updates tests accordingly.

Changes:

• Removed ExtractFrontmatterString and ExtractYamlChunk from frontmatter content extraction.
• Removed ComputeFrontmatterHash and ComputeFrontmatterHashWithExpressions from frontmatter hashing.
• Deleted/trimmed unit tests that exercised the removed functions and cleaned up now-unused imports.

Reviewed changes

Copilot reviewed 5 out of 5 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
pkg/parser/frontmatter_hash_test.go	Removes tests that directly targeted deleted hash APIs/helpers.
pkg/parser/frontmatter_hash_stability_test.go	Removes canonical-JSON verification that depended on deleted helpers; cleans up imports.
pkg/parser/frontmatter_hash.go	Deletes dead exported hash entrypoints; leaves remaining hash-from-file implementation in place.
pkg/parser/frontmatter_extraction_test.go	Removes tests for deleted YAML/frontmatter string extraction helpers; cleans up imports.
pkg/parser/frontmatter_content.go	Deletes dead frontmatter/YAML string extraction helpers.

Comments suppressed due to low confidence (1)

pkg/parser/frontmatter_hash.go:44

• buildCanonicalFrontmatter is still present, but after removing ComputeFrontmatterHash* there are no remaining references to it in the repo (only its definition remains). This contradicts the PR description (“remove … buildCanonicalFrontmatter”) and leaves dead code behind; either remove this helper entirely or reintroduce a caller that still needs it.

// buildCanonicalFrontmatter builds a canonical representation of frontmatter
// including all fields that should be included in the hash computation.
func buildCanonicalFrontmatter(frontmatter map[string]any, result *ImportsResult) map[string]any {
	canonical := make(map[string]any)

---

💡 Add Copilot custom instructions for smarter, more guided reviews. Learn how to get started.