feat(skills): add planning and milestone runner skills

[Mathews-Tom]

Summary

Adds two development workflow skills and registers them in the armory catalog:

• plan-prompts: generates .docs/DEVELOPMENT_PLAN.md and .docs/EXECUTION_PROMPTS.md from source documents, with source-traced milestones, command-backed verification, assumptions/gaps, and robust per-PR plus whole-stack review requirements in each generated /goal block.
• milestone-runner: executes milestone /goal blocks from .docs/EXECUTION_PROMPTS.md sequentially or in dependency-safe parallel waves, using external gates for PR state, CI/checks, verification commands, and review status before advancing. It only merges and cleans stacked branches when explicitly requested.

Also updates:

• README.md package count and Development & Tooling catalog rows.
• manifest.yaml generated package registry entries and complements.

Skill Evaluator Results

plan-prompts
Package: plan-prompts (skill)
  D1 Frontmatter Quality:            20/20
  D2 Trigger Coverage:               18/18
  D3 Structural Completeness:        16/20
  D4 Content Depth:                  18/22
  D5 Consistency:                    12/12
  D6 Compliance:                       8/8
  Overall:                          92/100 (92%)
  Status: PASS

milestone-runner
Package: milestone-runner (skill)
  D1 Frontmatter Quality:            20/20
  D2 Trigger Coverage:               18/18
  D3 Structural Completeness:        16/20
  D4 Content Depth:                  18/22
  D5 Consistency:                    12/12
  D6 Compliance:                       8/8
  Overall:                          92/100 (92%)
  Status: PASS

Validation

uv run python scripts/validate_evals.py
Validated 72 skills, 17 agents, 9 hooks, 6 rules, 7 commands, 3 utilities, 11 presets — all passed

uv run python scripts/validate_frontmatter.py
Validated 135 packages across 7 types — all passed

uv run python scripts/evaluate_package.py --path skills/plan-prompts
Overall: 92/100
Status: PASS

uv run python scripts/evaluate_package.py --path skills/milestone-runner
Overall: 92/100
Status: PASS

Commit structure

60cb8cb feat(skills): add plan-prompts package
d657ce6 docs(readme): list plan-prompts package
16f8b3b feat(skills): add milestone-runner package

Checklist

• SKILL.md has valid YAML frontmatter with name and description
• Skill name is kebab-case, under 64 characters
• Description is 200-1024 characters with trigger phrases and "Use when" clause
• No angle brackets or pushy language in description
• No secrets, credentials, or internal URLs in any file
• Tested locally with Claude Code
• All file references in SKILL.md resolve to existing files or user-provided project files
• Skill evaluator score is 70% or above
• No CRITICAL or HIGH findings from skill evaluator