[feature-runner] Explicit `/tdd` skill invocation and pinned `subagent_type` in step 4

[orioltf]

This was generated by AI during triage.

Parent

docs/issues/feature-runner/PRD.md

What to build

The Feature Runner's step 4 invokes /tdd via the Agent tool but does not pin subagent_type and does not instruct the sub-agent to explicitly load the /tdd skill. The current prompt template frames the sub-agent as "running /tdd in AFK mode" and relies on trigger-phrase auto-discovery to load /tdd's procedural guidance — an unreliable mechanism.

ADR-0029 ratifies replacing /tdd's planning phase with acceptance criteria. The rest of the skill (anti-horizontal-slicing, tracer-bullet loop, refactor-only-when-green, deep-modules / interface-design / refactoring sub-references) is still load-bearing and must be loaded deterministically.

Changes

1. SKILL.md step 4 — pin the subagent type.

Replace the current "invoke /tdd as a non-interactive sub-agent using the Agent tool" sentence with one that names the subagent type explicitly:

Invoke the sub-agent using the Agent tool with subagent_type: general-purpose — the only stock type with access to both the Skill tool (to load /tdd) and Edit/Write tools (to write code).

2. references/tdd-prompt-template.md — prepend an explicit skill invocation instruction.

At the top of the prompt body (before the AFK framing), add:

Begin by invoking the `tdd` skill via the Skill tool to load its full procedural guidance (red→green→refactor, vertical-slice rule, deep-modules / interface-design / refactoring sub-references). Then follow it using the acceptance criteria below as the pre-approved plan — the planning phase is complete; do not ask for confirmation.

3. docs/adr/0029-feature-runner-afk-invocation.md — amend the Consequences section.

Append:

The Feature Runner's prompt template explicitly instructs the sub-agent to invoke the tdd skill via the Skill tool, rather than relying on auto-discovery via trigger phrases. This makes the procedural-guidance load deterministic across Claude Code surfaces.

Acceptance criteria

• SKILL.md step 4 names subagent_type: general-purpose for the Agent call
• references/tdd-prompt-template.md opens with an explicit Skill-tool invocation instruction for tdd, placed before the AFK framing
• docs/adr/0029-feature-runner-afk-invocation.md Consequences section reflects the explicit-invocation policy
• The existing AFK framing ("The planning phase is complete — do not ask for confirmation") is preserved after the new instruction

Blocked by

None — can start immediately.

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PRD: docs/issues/feature-runner/PRD.md
Migrated from: docs/issues/feature-runner/16-explicit-tdd-skill-invocation.md (source removed after migration)
Touched by PRs: #25, #32