Bind implement-epic delegation to an installed repository-owned implement-ticket

[shaug]

Goal

Make the implement-epic transitive trust boundary explicit and testable: it may delegate only to an already-installed, readable, repository-owned implement-ticket with the expected terminal contract, and must never fetch or substitute a workflow at runtime.

Current evidence

implement-epic already requires implement-ticket to be available and readable and checks for ready_pr, ready_prs, merged, blocked, and requires_epic. The skills.sh Socket report nevertheless identifies a low-severity anomaly because the orchestration depends on a powerful subskill whose provenance is not stated as an enforceable runtime boundary.

Required behavior

Before selecting or mutating a child:

• verify that implement-ticket is already installed/readable through the host's normal skill mechanism;
• verify that its declared source is this repository-owned suite or an equivalent installation record that binds it to the same trusted distribution;
• verify the required terminal states and authority-preserving handoff contract;
• refuse a generic agent, a third-party same-name skill, an unreadable copy, an incompatible contract, or a dependency whose provenance cannot be established;
• never download, install, update, search for, or dynamically generate a substitute dependency during an epic run; and
• return blocked before child mutation with the exact missing, mismatched, or unverifiable dependency evidence.

Keep the check provider-neutral. Use existing installed-skill/source metadata when available and readable source identity otherwise. Do not introduce a package manager, network lookup, central registry, or runtime-specific mandatory API.

Evaluation and tests

Add deterministic/eval cases for:

1. a compatible repository-owned installed dependency;
2. a missing dependency;
3. a same-name third-party dependency;
4. a repository-owned dependency with an incompatible terminal contract;
5. a runtime that offers to download a replacement; and
6. provenance that cannot be established.

Only the first case may reach child selection or mutation. Every other case must return a precise blocked handoff without network installation or repository mutation.

Expected change surface

• skills/implement-epic/SKILL.md and directly related dependency/handoff references
• skills/implement-epic/evals/ cases and expectations
• focused validation tests where the skill has executable contract helpers
• README/CHANGELOG only where user-facing compatibility changes

Acceptance criteria

• implement-epic delegates only to an already-installed, readable, repository-owned compatible implement-ticket.
• Same-name third-party, missing, unreadable, incompatible, and unverifiable dependencies block before child mutation.
• The skill never downloads, installs, updates, searches for, or synthesizes a dependency at runtime.
• Dependency verification preserves the caller's authority ceiling and validates the expected terminal result contract.
• A valid existing installation retains the current epic workflow without an added mutation or review cycle.
• Positive and negative dependency-provenance cases are deterministic and result-blind.
• just format, just lint, and just test pass.

Non-goals

• Add a general skill package manager or dependency resolver.
• Pin every sibling skill to a single source commit when the installed distribution already establishes compatible provenance.
• Redesign implement-ticket, babysit-pr, carve-changesets, or review behavior.
• Change epic selection, graph semantics, completion policy, or authority ownership.
• Make network access available solely to verify dependency provenance.

[shaug]

Accepted and closing after verified merged delivery.

• PR: feat: bind epic delegation to trusted ticket skill #75
• Reviewed candidate: 569b11ec60977c19c66092690ffdada0dbac1eb4
• Merge commit on main: b2130dc742d6c81e50499eda4e4cc318ece471dc
• Validation: just format, just lint, and just test passed (501 tests); implement-epic forward evaluations passed 13/13
• Review/remote gates: exact-head repository review clean; CI passed; no unresolved reviews, comments, or threads
• Acceptance: installed repository-owned implement-ticket provenance and terminal contract are verified before child work; missing, third-party, incompatible, dynamically fetched, and unverifiable dependencies fail closed in result-blind executable evaluations

The accepted outcome is represented on current main.