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>

hermes_cli/web_server.py

@@ -838,6 +838,10 @@ def _spawn_hermes_action(subcommand: List[str], name: str) -> subprocess.Popen:
         popen_kwargs["start_new_session"] = True
 
     proc = subprocess.Popen(cmd, **popen_kwargs)
+    # The child inherits its own duplicated fd for stdout/stderr, so the
+    # parent's handle can be released immediately — otherwise we leak one
+    # fd per spawned action.
+    log_file.close()
     _ACTION_RESULTS.pop(name, None)
     _ACTION_PROCS[name] = proc
     return proc
@@ -1808,6 +1812,11 @@ async def remove_env_var(body: EnvVarDelete):
         return {"ok": True, "key": body.key}
     except HTTPException:
         raise
+    except ValueError as exc:
+        # remove_env_value raises ValueError for invalid key names. Surface
+        # the message to the SPA so the user understands why the delete was
+        # refused instead of seeing an opaque 500. Mirrors PUT /api/env.
+        raise HTTPException(status_code=400, detail=str(exc)) from exc
     except Exception:
         _log.exception("DELETE /api/env failed")
         raise HTTPException(status_code=500, detail="Internal server error")