refactor: daemon collectors, thin webui proxies, pure config reads

- move state collectors from lib/state.py to daemon/collectors/ (7
  modules, registration side-effect; daemon/server.py imports the
  package before the first populate())
- webui/api: new daemon_route() decorator factory in common.py
  collapses the try/except daemon-proxy boilerplate in all 8
  blueprints (rules/params/body/transform keep responses identical)
- firewall: interface-coverage invariant — config is the source of
  truth for zone interfaces (absent key = empty, no hands-off
  zones); pure validate_coverage() enforced at save (400) and apply
  (409, force: true overrides), top-level `unmanaged` exemption
- lib: get_config() reads are now pure (no dir creation or writes);
  new lib/bootstrap.py creates runtime dirs and persists the
  one-shot nginx legacy migration at daemon start, after
  system_import (lib.nginx.migrate_config_file)
- lib/common: compute_pending() apply-bookkeeping helper
- daemon: emit_and_refresh() handler helper; refresh_state(bump=) so
  /status/refresh no longer bumps versions (poll/mutation only)
- acme: move --log last so acme.sh never treats a real arg as the
  log-file argument
- docs: AGENTS.md, config.md, state-model.md, api.md updated;
  HARDEN.md dropped (plan implemented); apply-confirm force wording

Tests: 917 passed; ruff check + format clean.

lib/dnsmasq.py

@@ -37,8 +37,12 @@ DEFAULT_CFG: dict[str, Any] = {
 
 
 def get_config() -> dict[str, Any]:
-    """Load current dnsmasq config from JSON state file."""
-    ensure_dirs(CONFIG_DIR, DATA_DIR, FRAGMENTS_DIR)
+    """Load current dnsmasq config from JSON state file.
+
+    Pure read — never writes or creates directories. Returns the in-memory
+    default when the file is missing; directories and the file are
+    materialized on the first ``save_config``.
+    """
     raw = load_json(CONFIG_PATH)
     if not raw:
         return deepcopy(DEFAULT_CFG)
@@ -73,6 +77,11 @@ def set_domain(domain: str | None) -> None:
 
 
 __all__ = [
+    "CONFIG_DIR",
+    "CONFIG_PATH",
+    "DATA_DIR",
+    "DEFAULT_CFG",
+    "FRAGMENTS_DIR",
     "get_config",
     "save_config",
     "set_domain",