tools: the write guard reaches the three flags named something other than --json

The write-axis leg grades ONE surface per tool: `--json PATH`. Measured at
c3ffee9 with caller_write_flags.py (asset below), tools/ offers 22 flags a
caller can aim for a write, across 21 tools: 19 are `--json` -- guarded, and
graded by the leg -- and three are named otherwise, none of them wrapped:

  tools/queue_index.py      :581   --write       BARE
  tools/tool_map.py         :510   --write       BARE
  tools/doc_census_check.py :1831  --save-vocab  BARE

BARE = `open(path, "w")` with no try. Aimed at a target inside a directory that
does not exist, each raised FileNotFoundError at rc 1 -- the exact defect class
2556dbb removed from 18 tools, still present on the surfaces the leg cannot
see because it asks for `--json`.

Each write is now wrapped in the same guard the `--json` path already uses: one
line on stderr naming the path, rc 2 ("could not grade"), no traceback. Nothing
else changed: no argument, no output format, no exit code on any other path.

VERIFIED, both directions, in a throwaway worktree (never this tree):
  /root/.hermes/wizard-outputs/volt/2026-10-21-write-axis-bites/write_flag_probe.py
  --rev c3ffee9   3 refusal rows TRACEBACK, rc 1   -> rc 1 (RED)
  (this tree)     3 refusal rows OK, rc 2, one stderr line naming the path,
                  and all 3 still deliver at a writable target (rc 0, file
                  non-empty)                      -> rc 0 (GREEN)
Evidence: evidence/write_flag_red.json, evidence/write_flag_green.json.

Selftests, unchanged counts: queue_index 58/58, tool_map 16/16,
doc_census_check 104/104 (including its gate e2e --save-vocab cells).
repo gate: 6 legs, 6 pass, 0 fault, rc 0 (selftest-sweep 21 tools 0 fatal).

REMAINING BLIND SPOT, stated so it is not read as closed: write_probe.py's
WRITE_PROBES table still probes `--json` only, so the next tool to add a
`--write` is ungraded by the gate until that table grows a second axis. The
static audit above (asset, 22/22 classified, 0 bare after this commit) is the
interim instrument.

tools/doc_census_check.py

@@ -1828,10 +1828,15 @@ def main():
             units[name].update(k for k in entry[0][0] if k in keep)
         observed = sum(len(v) for v in seen.values())
         kept = sum(len(v) for v in units.values())
-        with open(a.save_vocab, "w", encoding="utf-8") as fh:
-            json.dump({"rev": a.rev, "repo": a.repo,
-                       "tools": {k: sorted(v) for k, v in units.items()}},
-                      fh, indent=1, sort_keys=True)
+        try:
+            with open(a.save_vocab, "w", encoding="utf-8") as fh:
+                json.dump({"rev": a.rev, "repo": a.repo,
+                           "tools": {k: sorted(v) for k, v in units.items()}},
+                          fh, indent=1, sort_keys=True)
+        except OSError as exc:
+            print("cannot write --save-vocab " + a.save_vocab + ": " + str(exc),
+                  file=sys.stderr)
+            return 2
         print(f"wrote vocabulary {a.save_vocab}: {len(units)} tool(s), "
               f"{kept} unit(s) at {a.rev} ({observed} key(s) observed, "
               f"{observed - kept} unspendable by any claim)")

tools/queue_index.py

@@ -578,8 +578,12 @@ def run(args):
         return 0
 
     if args.write:
-        with open(args.write, "w", encoding="utf-8") as fh:
-            fh.write(build_doc(payload))
+        try:
+            with open(args.write, "w", encoding="utf-8") as fh:
+                fh.write(build_doc(payload))
+        except OSError as exc:
+            print("cannot write --write " + args.write + ": " + str(exc), file=sys.stderr)
+            return 2
         print("wrote %s (%d bytes)" % (args.write, os.path.getsize(args.write)))
         return 0
 

tools/tool_map.py

@@ -507,8 +507,12 @@ def main():
         print(f"tool_map: wrote {args.json}")
 
     if args.write:
-        with open(args.write, "w", encoding="utf-8") as fh:
-            fh.write(text)
+        try:
+            with open(args.write, "w", encoding="utf-8") as fh:
+                fh.write(text)
+        except OSError as exc:
+            print("cannot write --write " + args.write + ": " + str(exc), file=sys.stderr)
+            return 2
         print(f"tool_map: wrote {args.write} ({len(text)} B, "
               f"{len(data['rows'])} tools, {len(data['legs'])} gate legs)")
         return 0