feat(tooling): Implement Deterministic Issue Sealing Script and Project Metadata Sync

🎯 1. Objective & Scope

Implement automated CLI tooling to eliminate premature issue creation and narrative metadata pollution:

1. scripts/seal-issue.sh: Deterministic Bash script to seal issues from local implementation plans (implementation_plan.md), bind native milestones (--milestone), link native sub-issues (--parent), and initialize Epic branches.
2. scripts/sync-project-metadata.mjs: Node.js ESM utility interfacing with GitHub Projects v2 GraphQL API to populate custom fields (Priority, Size, Estimate, Status, Cycle).
3. Update docs/scripts-reference.md and register the new tools in Category 8 of scripts/validate-docs.sh.

🏛️ 2. Architectural Bounds & Invariants

• Parent Epic: epic(governance): establish just-in-time issue sealing, native project metadata sync, and isolated epic branching protocol #12 (epic(governance): establish just-in-time issue sealing...)
• PR Base Target: epic/issue-12-jit-sealing-epic-protocol
• Release Mode: Silent (skip-release label required)
• Data & Privacy: Zero PII, local CLI execution only, official gh auth credentials.
• Byte Budgets:
  • scripts/seal-issue.sh < 8,000 bytes.
  • scripts/sync-project-metadata.mjs < 6,000 bytes.
  • scripts/validate-docs.sh < 9,500 bytes.
  • docs/scripts-reference.md < 13,000 bytes.

📋 3. Acceptance Criteria

• ./scripts/seal-issue.sh --from-plan accurately parses YAML frontmatter and extracts the clean markdown body.
• Supports --dry-run to simulate sealing without remote mutations.
• Natively passes --parent <epic_id> when parent is defined in frontmatter.
• Natively passes --milestone "<milestone>" when defined.
• Invokes scripts/sync-project-metadata.mjs to set Priority, Size, Estimate, Status on Project feat(governance): align project metadata triad with native GitHub Projects v2 fields #2.
• Automatically creates and pushes epic/issue-<id>-<slug> when type == epic or size in [L, XL].
• Updates local implementation_plan.md with generated issue ID, branch name, and approved status.
• ./scripts/validate-docs.sh passes 100% with both scripts verified in Category 8.
• ./scripts/quality-check.sh passes with 0 errors and 0 lint warnings.