feat: harden workflow gates and expose token usage

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

@@ -151,9 +151,13 @@ 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),
+2. Load the artifacts produced so far with `tht session documents <id> --json`, which
+   returns their keys and contents directly: `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`.
+   **Non cercare i file fisici con `find`, `ls`, `cat` o il generic read tool**: the
+   session repository may live outside the checkout and the documents command is the
+   canonical read boundary.
 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.