chore: establish SpecGit delivery harness

[LeXwDeX]

Why

The authoritative DAG template repository has no SpecGit policy, so delivery cannot produce an auditable specgit finish verdict even though its CI has a stable validation check.

Scope

Add the minimal SpecGit harness configured to require the existing Validate DAG templates check. Do not change workflow templates or runtime compatibility in this issue.

Approach

Initialize SpecGit from the repository root, preserve the existing GitHub Actions validation workflow, and verify specgit doctor --json succeeds.

Acceptance

• specgit doctor --json reports a healthy policy.
• The policy requires Validate DAG templates.
• Existing template validation CI remains unchanged and passes on the PR.

[LeXwDeX]

SpecGit delivery branch: feat/17-specgit-harness (draft pull request #18).

[LeXwDeX]

SpecGit delivery branch: feat/17-specgit-harness (draft pull request #20).

[LeXwDeX]

Implemented on chore/17-specgit-harness (PR #21). Decision: the policy records the canonical check id validate — the job id of the Validate DAG templates workflow (check-run names carry the job id, not the display name). Harness generated by specgit init --required-check validate --no-protect; specgit doctor --json exits 0; existing validate.yml and runtime-compat.json untouched.

[LeXwDeX]

Acceptance evidence (PR #21, head aa825cc): specgit doctor --json exit 0; policy requires canonical check id validate; validate and SpecGit Acceptance both pass on the PR; specgit finish --json exit 0 (accepted, 11/11 gates). One required repo-side reconciliation: the route-catalog inventory now skips hidden dotfiles so the committed .specgit.yaml binding does not collide with the 16-route catalog — guarded by two new tests; no route template, runtime-compat.json, or workflow file was modified.