fix: batch of small robustness/correctness fixes from @kyssta-exe

Salvages 8 distinct fixes from a batch of PRs by @kyssta-exe, reapplied
onto current main (original branches were stale) with a few refinements.

- cron(jobs.py): load_jobs() validates top-level JSON shape — a bare
  list auto-repairs into the {"jobs": [...]} dict; scalars/null raise a
  clear RuntimeError instead of an uncaught AttributeError that took
  down the whole cron subsystem (#37065, closes #36867).
- web(web_server.py): close the per-action log file handle after Popen
  so the parent stops leaking one fd per spawned action (#36843).
- web(web_server.py): DELETE /api/env returns 400 for invalid key names
  instead of a misleading 500, mirroring PUT /api/env (#36840).
- gateway(gateway.py): read /proc/<pid>/cmdline inside a with-block so
  the fd is released immediately instead of relying on GC (#36804).
- web-tools(web_tools.py): include "xai" in check_web_api_key() so a
  configured X.AI web backend reports as available (#36802).
- compression(conversation_compression.py): mark the feasibility check
  done only after it completes, and default the gate to "not checked"
  if the attribute is missing (#36803).
- completion(completion.py): replace `ls` with directory globbing in the
  generated bash/zsh/fish profile listers — handles names with spaces
  and skips non-directory entries (#36806).
- terminal-tool(terminal_tool.py): drop a duplicate `import threading`
  (#36808).
- claw(claw.py): the migrate recommendation now points at the real
  `hermes gateway stop` command instead of the non-existent
  `hermes stop` (#36795, #36796, closes #36771).
- tests: guard against a leaked HERMES_CRON_SESSION breaking gateway
  approval tests — add it to the hermetic conftest unset list (root
  cause, protects every test) and pop it in the affected test's
  setup_method (#36796).

Co-authored-by: kyssta-exe <kyssta-exe@users.noreply.github.com>

tests/tools/test_approval.py

@@ -1395,11 +1395,16 @@ class TestApprovalTimeoutIsNotConsent:
 
         self._saved_env = {
             k: os.environ.get(k)
-            for k in ("HERMES_GATEWAY_SESSION", "HERMES_YOLO_MODE",
+            for k in ("HERMES_GATEWAY_SESSION", "HERMES_CRON_SESSION",
+                      "HERMES_YOLO_MODE",
                       "HERMES_SESSION_KEY", "HERMES_INTERACTIVE")
         }
         os.environ.pop("HERMES_YOLO_MODE", None)
         os.environ.pop("HERMES_INTERACTIVE", None)
+        # HERMES_CRON_SESSION takes priority over HERMES_GATEWAY_SESSION in
+        # _is_gateway_approval_context(); a leaked value from a parent cron
+        # process would force the cron path and break these gateway tests.
+        os.environ.pop("HERMES_CRON_SESSION", None)
         os.environ["HERMES_GATEWAY_SESSION"] = "1"
         os.environ["HERMES_SESSION_KEY"] = self.SESSION_KEY