t.2p4: add dynamic task subtree insertion for ace-assign

[cs3b]

📋 Summary

Assignment workflows can now insert multiple steps from a YAML file in a single command with ace-assign add --from <file>. Before this, adding a task subtree into a running assignment required multiple manual add calls or pre-building the entire assignment upfront. Now, mid-flight composition is a one-liner that preserves metadata, expands nested sub_steps, and slots new steps at the right queue position.

✏️ Changes

• Add --from <file> flag to ace-assign add: reads a YAML step list and batch-inserts all entries with sequential numbering, metadata passthrough, and sub_steps expansion (d6b3f9c)
• Add CLI validation: --from and positional name are mutually exclusive; missing file and empty steps: produce explicit errors (d6b3f9c)
• Add AssignmentExecutor#add_batch: reuses existing single-add behavior in a loop, preserving added_by: batch_from:<filename> metadata on every inserted step (d6b3f9c)
• Add as-assign-add-task canonical skill and wfi://assign/add-task workflow for guided subtree insertion (d487839, ee0771d, 9fcdef2)
• Add provider skill projections for Claude, Codex, Gemini, OpenCode, and Pi (d487839, 9fcdef2)
• Update docs (usage, getting-started, handbook) covering the new add --from workflow (d6b3f9c)

📁 File Changes

 +789,   -20   22 files   total

 +618,   -17   11 files      ace-assign/
 +218,   -16    3 files   🧱 lib/
  +67,   -11                 ace/assign/cli/commands/add.rb
 +150,    -4                 ace/assign/organisms/assignment_executor.rb
   +1,    -1                 ace/assign/version.rb
 +207,    -0    2 files   🧪 test/
 +107,    -0                 commands/add_command_test.rb
 +100,    -0                 organisms/assignment_executor_test.rb
 +171,    -0    2 files   📚 handbook/
  +24,    -0                 skills/as-assign-add-task/SKILL.md
 +147,    -0                 workflow-instructions/assign/add-task.wf.md
  +22,    -1    4 files      
  +13,    -0                 CHANGELOG.md
   +2,    -0                 docs/getting-started.md
   +2,    -0                 .../handbook.md
   +5,    -1                 .../usage.md

   +7,    -2    3 files      ace-overseer/
   +1,    -1    1 files   🧱 lib/
   +1,    -1                 ace/overseer/version.rb
   +6,    -1    2 files      
   +5,    -0                 CHANGELOG.md
   +1,    -1                 ace-overseer.gemspec

  +24,    -0    1 files      .claude/skills/as-assign-add-task/SKILL.md
  +24,    -0    1 files      .codex/skills/as-assign-add-task/SKILL.md
  +24,    -0    1 files      .gemini/skills/as-assign-add-task/SKILL.md
  +24,    -0    1 files      .opencode/skills/as-assign-add-task/SKILL.md
  +24,    -0    1 files      .pi/skills/as-assign-add-task/SKILL.md
  +13,    -0    1 files      CHANGELOG.md

🧪 Test Evidence

• AddCommandTest (new, 107 lines) — validates --from flag handling: mutual exclusivity with name, missing file error, empty steps error, and successful batch insertion output
• AssignmentExecutorTest (new, 100 lines) — validates add_batch behavior: sequential insertion, metadata passthrough (added_by, context, skill), sub_steps expansion, and child rebalance
• Suite totals: 488 tests, 1547 assertions, 0 failures, 0 errors (ace-assign)
• Monorepo: 7482 tests passed, 1 pre-existing failure (ace-docs, unrelated)

📦 Releases

• ace-assign v0.38.0 — Add --from <file> batch insertion, as-assign-add-task skill/workflow, docs updates
• ace-overseer v0.11.1 — Bump ace-assign dependency to ~> 0.38
• Root v0.9.926 — Coordinated release entry

🎮 Demo

Run

# Create a YAML file with steps to insert
cat > /tmp/subtree.yml << 'EOF'
steps:
  - name: onboard
    skill: as-onboard
    instructions: Load project context
  - name: implement
    skill: as-task-work
    instructions: Work on the task
    context: fork
EOF

# Insert into a running assignment after step 010
ace-assign add --from /tmp/subtree.yml --after 010 --assignment <id>

Expected Output

Added step 011 (onboard) after 010
Added step 011.01 (implement) [fork] after 011