docs sync + revert auto-unfree removal

revert the earlier 'operator must set allowUnfree' move:
per-agent containers evaluate their own nixpkgs and the operator's
host-level allowUnfree doesn't propagate in. restoring the scoped
allowUnfreePredicate inside both the claude-unstable overlay and
harness-base.nix; documented in README + gotchas as 'nothing to
set on the operator side'.

docs:
- claude.md file map adds crash_watch.rs, kick_agent on coordinator,
  /api/model + journald viewer + bind-with-retry references.
- scratchpad rewritten to reflect the recent run.
- web-ui.md: notification row + browser notifications section,
  state row (badge + model chip + last-turn chip + cancel button),
  per-agent inbox, /model slash, /cancel-question + journald
  endpoints, focus-preservation on refresh.
- turn-loop.md: --model is read from Bus::model() per turn (runtime
  override via /model); recv(wait_seconds) up to 180s with the
  rationale; ask_operator gains ttl_seconds; new TurnState section;
  kick_agent inbox-on-startup hint.
- approvals.md: ttl/cancel resolution paths for operator questions.
- persistence.md: /state/hyperhive-model file.
- gotchas.md: web UI port collision policy (rename, don't probe);
  bind retry + SO_REUSEADDR shape; auto-unfree restored.
- todo.md: cleaned up empty sections and stale entries; /model
  shipped, dropped from the list.

flake.nix

@@ -67,14 +67,16 @@
         claude-unstable =
           final: prev:
           let
-            # Inherit the *user's* nixpkgs config so allowUnfree (or an
-            # `allowUnfreePredicate` they set on their flake) propagates
-            # into the unstable import. hyperhive does not silently
-            # bypass the unfree gate — if the operator hasn't opted in,
-            # this overlay's `claude-code` access fails honestly.
+            # The overlay imports its own nixpkgs-unstable instance to
+            # pin claude-code there. That instance has its own config
+            # (independent from the user's prev.config), so we have to
+            # set allowUnfreePredicate inline to whitelist claude-code
+            # specifically — otherwise the unstable import itself
+            # refuses to evaluate. This is scoped: only claude-code
+            # bypasses unfree, nothing else.
             unstable = import nixpkgs-unstable {
               inherit (prev.stdenv.hostPlatform) system;
-              config = prev.config;
+              config.allowUnfreePredicate = pkg: builtins.elem (prev.lib.getName pkg) [ "claude-code" ];
             };
           in
           {