ext-keybindings: hot-reload unbox.toml (live config, no restart)

Editing the config now re-applies keybindings live, via the kernel's watch_file
service. In activate() we watch the effective config path (the create() arg, else
~/.config/unbox/unbox.toml) — even if it doesn't exist yet, so creating it later is
picked up — holding the FileWatch as a member. On change, reload_config() re-reads
+ re-parses (the existing pure toml core) and SWAPs the live binding table the
key_filter link matches against (matcher_), so new bindings apply with no
re-subscribe. A malformed / unreadable / mid-edit-broken file KEEPS the current
bindings and logs one warning — the session never loses working keys, never throws.

Real-seat verified: editing the command (fuzzel->foot) logged "config reloaded
(5 binding(s))" live; a deliberately broken file logged "reload failed; keeping
current bindings" with the session staying ALIVE; restoring it recovered. Added a
pure reload-semantics doctest (A->B swap; malformed keeps prior). ext-keybindings
2/2 green on build + build-asan. Edits confined to packages/ext-keybindings/.

1 files changed, 21 insertions, 0 deletions

diff --git a/packages/ext-keybindings/src/config.cpp b/packages/ext-keybindings/src/config.cpp
index 4d1045f..726b24b 100644
--- a/packages/ext-keybindings/src/config.cpp
+++ b/packages/ext-keybindings/src/config.cpp
@@ -101,4 +101,25 @@ auto load_from_string(std::string_view toml_text) -> LoadResult {
     return result;
 }
 
+auto reload_bindings(const std::vector<policy::Binding>& current, std::string_view toml_text)
+    -> ReloadDecision {
+    ReloadDecision decision;
+    LoadResult loaded = load_from_string(toml_text);
+    decision.warnings = std::move(loaded.warnings);
+
+    // KEEP-OLD on a syntax error or on a parse that produced no usable bindings
+    // (an empty file, a [[keybind]]-less doc, or one where every entry was
+    // skipped). Either way the live table must remain the user's working keys.
+    if (loaded.parse_error || loaded.bindings.empty()) {
+        decision.bindings = current; // unchanged copy
+        decision.swapped = false;
+        return decision;
+    }
+
+    // SUCCESS: the new table replaces the live one (the swap).
+    decision.bindings = std::move(loaded.bindings);
+    decision.swapped = true;
+    return decision;
+}
+
 } // namespace unbox::ext_keybindings::config