fix(taskctl): adversarial-developer feedback loop loses context between rounds, causing rewrite loops

[randomm]

Critical Bug

After 3 rounds of adversarial review, the same critical issues keep appearing in different forms. The developer-adversarial loop fails to converge because developer does not receive context about previous implementation attempts.

Evidence

Round 1: CRITICAL - Branch regex allows command injection
Round 2: MEDIUM - Branch regex too restrictive, rejects valid names
Round 3: CRITICAL - Branch regex still has flaws (empty strings, invalid chars)

Same regex issue appears differently each round. Each "fix" introduces NEW bugs.

Root Cause Analysis

What IS passed between rounds:

• verdict.summary - brief description
• verdict.issues - list with location/severity/fix
• verdict.tested_scenarios - what was tested
• verdict.coverage_level - confidence
• Attempt number: "This is retry X of Y"

What is MISSING (CRITICAL GAP):

• Git diff showing previous implementation
• No file list of what was already changed
• No visibility into "what did I already try"

Why the loop didn't converge:

The prompt tells developer "codebase changes are already in worktree" but developer never sees WHAT changed. Each retry, developer works blind - rewrites code from scratch instead of fixing specific bugs. This introduces NEW issues in each round.

Source: packages/opencode/src/tasks/pulse-scheduler.ts:537-566 (respawnDeveloper)

How to Reproduce

1. Run taskctl start on any issue
2. Wait for developer to complete and adversarial to find issues
3. Watch respawnDeveloper prompt - it lists issues but shows NO git diff
4. Developer rewrites code instead of fixing bugs
5. Adversarial finds NEW issues in round 2
6. Repeat until max attempts exhausted

Recommended Fix

Add git diff output to respawnDeveloper prompt:

// In respawnDeveloper (pulse-scheduler.ts ~line 537-566)

const diffOutput = await $`git diff ${validatedBaseCommit}..HEAD`
  .cwd(worktreeInfo.directory)

const previousImplementation = `# PREVIOUS IMPLEMENTATION (for reference)

The following changes were previously committed in this worktree:

\`\`\`bash
${diffOutput}
\`\`\`

⚠️ CRITICAL: These changes already exist. Do NOT rewrite from scratch.
Read the changed files FIRST, then fix the specific issues listed below.
`

// Include this in the prompt before listing adversarial issues

Files Affected

• packages/opencode/src/tasks/pulse-scheduler.ts - respawnDeveloper function

Quality Gates (Non-Negotiable)

• TDD: Write test verifying git diff is included in respawn prompt
• Coverage: 80%+ for modified code paths
• Local verification: All tests pass

Acceptance Criteria

• Developer receives git diff of previous implementation on retry
• Adversarial feedback loop converges within 2 rounds for common issues
• No NEW issues introduced in round 2 that stem from lack of context
• Developer prompt explicitly shows what already exists before listing fixes