refactor(supervise): make Supervisor a service class the orchestrator calls

Turn the loose queue/audit functions in orchestrator/supervisor/queue.py into
methods on a concrete Supervisor service. The Orchestrator now owns an
injectable `self._supervisor` and calls `self._supervisor.write_proposal(...)`
etc., instead of module-level free functions — the supervise dependency is
explicit and mockable, and a Supervisor can be scoped to a `db_path` (defaults
to the host DB) so tests can point it at a temp database.

  - Supervisor (in the package __init__) drops the ABC and gains write_proposal,
    read_proposal, list_pending_proposals, list_all_pending_proposals,
    write_response, read_response, archive_all_proposals, write_audit_entry,
    read_audit_entries, plus the launch-time prepare().
  - render_diff / sha256_hex are pure and stateless, so they move to
    orchestrator/supervisor/util.py (re-exported from the facade) rather than
    becoming methods.
  - queue.py is deleted; service.py + the supervise tests call through a
    Supervisor instance.

Full unit suite green (2243).

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

bot_bottle/orchestrator/supervisor/util.py

@@ -0,0 +1,31 @@
+"""Pure supervise helpers — diff rendering and content hashing.
+
+Stateless utilities used alongside the `Supervisor` service. Kept as plain
+functions (not methods) because they carry no state and are also handy to
+callers that only need to hash or diff.
+"""
+
+from __future__ import annotations
+
+import difflib
+import hashlib
+
+
+def render_diff(before: str, after: str, *, label: str = "config") -> str:
+    """Unified diff suitable for the audit log + TUI. Empty diff (no changes)
+    renders as the empty string."""
+    diff = difflib.unified_diff(
+        before.splitlines(keepends=True),
+        after.splitlines(keepends=True),
+        fromfile=f"{label} (current)",
+        tofile=f"{label} (proposed)",
+        lineterm="",
+    )
+    parts = list(diff)
+    if not parts:
+        return ""
+    return "".join(p if p.endswith("\n") else p + "\n" for p in parts).rstrip("\n")
+
+
+def sha256_hex(content: str) -> str:
+    return hashlib.sha256(content.encode("utf-8")).hexdigest()