Execute epic with budget tracking

Execute Epic phases with design review, implementation, and verification

Executing a multi-phase Epic with parallel design/implementation review and human checkpoints at budget/escalation gates.

• · epic_path: path to Epic definition file
• · epic_slug: short name for evidence storage
• · phase_number: integer (1+)
• · phase_name: human readable phase name
• · handoff_path: where to write design handoff
• · completion_path: where to write implementation completion
• · grounding_path: optional override for grounding file
• · reviewer_count: number of parallel reviewers (default 2)
• · steps: array of 'design', 'review', 'implement', 'impl_review' to run

• · HANDOFF.md with YAML frontmatter (task_type, e2e_required, research_required, git_tracked_dirs, Acceptance Criteria)
• · COMPLETION.md with files_changed, commit_message, layer1_passed verdict
• · evidence files (design review, impl review findings with P0/P1/P2 counts)
• · budget consumption report

• · Epic template files (.tad/templates/handoff-a-to-b.md, completion template)
• · Conductor task system
• · parallel reviewers (Alex, Blake agents)

• · Epic file exists at epic_path with Phase N detail block
• · Grounding file exists (or created from git state)
• · Handoff template available at .tad/templates/handoff-a-to-b.md
• · Steps array is non-empty and contains valid step names

• · First design attempt <50 lines → re-spawn Alex design agent (loop until >= 50 lines)
• · Reviewer P0 findings block implementation → Blake waits for resolution
• · Implementation exceeds budget → escalation to human checkpoint before continuing
• · layer1_passed=false → implementation reviewers notified, evidence added to task

• · YAML frontmatter enforces structured handoff (task_type, requirements, acceptance criteria)
• · Design must be >= 50 lines (enforces completeness before review)
• · Parallel reviewers (not sequential) reduce phase latency
• · Budget reporting at each checkpoint (tokens, escalations visible to human)
• · Evidence stored per epic_slug for review audit trail