docs: canonicalize doc approval pipeline

[enricopiovesan]

Summary

Records Decision 19 and approves its derived Spec 069: the doc-approval
pipeline uses the existing analyze contract followed by recommend, and
does not add a duplicate extract public capability.

Governing Spec

• 004-spec-alignment-gate
• 058-workflow-pipeline-execution
• 065-sigstore-bundle-verification
• 069-doc-approval-pipeline-canonicalization

Project Item

Closes #538

Definition of Done

• Decision 19 records the accepted canonical pipeline.
• Spec 069 preserves analyze@1.0.0 compatibility and defines analyze -> recommend.
• The approved-spec registry covers the resulting implementation paths.
• Add doc-approval.recommend WASM agent for pipeline showcase #555 and App Reference Template executable capability package manifests and deterministic build commands #111/Document adapter responsibilities versus core runtime responsibilities #112 are linked as follow-on implementation.

Validation

• git diff --check
• jq empty specs/governance/approved-specs.json
• bash scripts/ci/spec_context_check.sh
• BASE_SHA=origin/main bash scripts/ci/spec_alignment_check.sh /private/tmp/issue-538-pr-body.md