docs(harness): add Phase 0 Resume cold-start procedure to the orchestrator skill

harness/.pi/skills/tht-sessione/SKILL.md

@@ -73,6 +73,25 @@ about a domain term, ask the reviewer.
     phase N **reviewing the existing artifacts**; `tht phase reopen` deletes artifacts
     beyond the target. Do NOT re-run `tht` commands for artifacts that are still valid.
 
+## Phase 0 — Resume (cold start)
+
+When launched with `/riprendi-sessione <id>` you have NO prior conversation — the
+persisted state is your only context. Bootstrap before doing anything else:
+
+1. `tht session show <id> --json` → read `phase` (the current phase N), `status`, and
+   the manifest (`question`, `database`, `schema`).
+2. Load the artifacts produced so far, as needed for phase N: `question.md` (revised
+   question), `schema_linking.json` (F4 output), `ctes/*.sql` + `cte_tests.json` (F6),
+   `sql_final.sql` (F7). The decision ledger is summarized by `tht session show`.
+3. **Resume at phase N reviewing the existing artifacts** (same discipline as rollback,
+   §Disciplines 11). Do NOT restart from Phase 1, do NOT re-run `tht` commands for
+   artifacts that already exist and are valid, and do NOT treat this as a new question.
+4. Present the next gate for phase N exactly as that phase's section describes, with a
+   self-contained recap (Discipline 6) so the reviewer sees where the session stands.
+
+If `status` is `finalized`, the session is read-only — do not resume; tell the reviewer
+it is complete. (The backend already refuses resume for finalized/archived sessions.)
+
 ## Phase 1 — Clarification
 
 Prerequisite: you must already be in Phase 1.