docs(options): README tables reconciled + permanent option-docs check (item 6a)

Slice (a) of the docs review: 9 undocumented nomarchy.* options got
README rows or inline .leaf mentions (autoTimezone, camera IR-hide,
intel.guc, amd.pstate/vaapi, package, system.stateFile, restic.paths).
The diff is now a flake check: option names are eval-walked from the
four option-declaring modules (config halves stay lazy) and compared
to the tables by tools/check-option-docs.py — undocumented options and
stale table rows both fail. Negative-tested against the pre-fix README
(reports exactly the 9 gaps). Item 6 split into slices a–d in BACKLOG.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

tools/check-option-docs.py

@@ -0,0 +1,60 @@
+#!/usr/bin/env python3
+"""Option-surface ↔ README drift check (flake check `option-docs`).
+
+Usage: check-option-docs.py <option-surface.txt> <README.md>
+
+<option-surface.txt> is one full option path per line (nomarchy.…),
+generated at eval time in flake.nix by walking the four option-declaring
+modules — so the "live surface" side can never go stale by itself.
+
+Two directions:
+
+1. Every live option must be documented in the README: either its full
+   path appears verbatim (a table row), or — for sub-knobs that don't end
+   in `.enable` — a backticked `.leaf` shorthand appears somewhere (the
+   convention for tuning knobs documented inline in their parent row,
+   e.g. nightlight's `.temperature`). `.enable` options always get their
+   own row: the shorthand `` `.enable` `` would match any of them.
+
+2. Every `nomarchy.*` path in a README option-table row (lines starting
+   `| `nomarchy.`) must still exist — catches rows for renamed/removed
+   options.
+"""
+
+import re
+import sys
+
+surface_file, readme_file = sys.argv[1], sys.argv[2]
+
+surface = [l.strip() for l in open(surface_file) if l.strip()]
+readme = open(readme_file).read()
+
+# Backticked `.leaf` shorthands present in the README (inline sub-knob docs).
+shorthands = set(re.findall(r"`(\.[A-Za-z][A-Za-z0-9]*)`", readme))
+
+failures = []
+
+for opt in surface:
+    if opt in readme:
+        continue
+    leaf = "." + opt.rsplit(".", 1)[1]
+    if leaf != ".enable" and leaf in shorthands:
+        continue
+    failures.append(
+        f"undocumented option: {opt} — add a README table row"
+        + ("" if leaf == ".enable" else f" or an inline `{leaf}` mention")
+    )
+
+# Reverse: option paths claimed by table rows must exist.
+for line in readme.splitlines():
+    m = re.match(r"\|\s*`(nomarchy\.[A-Za-z0-9.]+)`", line)
+    if m and m.group(1) not in surface:
+        failures.append(f"stale README table row: {m.group(1)} is not a live option")
+
+if failures:
+    print(f"option-docs: {len(failures)} problem(s)")
+    for f in failures:
+        print("  " + f)
+    sys.exit(1)
+
+print(f"option-docs: {len(surface)} options all documented, no stale rows")