Add bulk clear-params action that re-extracts from retained logs (ticket 052)

DELETE /api/params clears the entire standalone-param set — manual and
auto-derived alike — then immediately re-runs auto_declare_params against
every IndexKey::IngestedLog entry still held in the engine's index (oldest
to newest), so params come back fresh from currently-retained log text
without requiring new lines to be ingested. This is a deliberate full
reset, unlike reload_engine_declarations's profile-switch cleanup, which
preserves auto-derived params since those are engine-discovered facts
rather than profile state; here the immediate re-extraction step makes
clearing them safe.

Settings::clear_param_declarations empties the active profile's persisted
params so they don't reappear on restart. The webapp's Params section gets
a single "Clear all" button (with a confirm dialog and a status line
reporting removed/re-derived/logs_considered) rather than a per-param
delete loop; logs_considered surfaces that lines already evicted by
max_logs can't regain their params.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01XFUNZwCvz3kcod3352ZR2o

src/profile.rs

@@ -600,6 +600,26 @@ impl Settings {
         Ok(())
     }
 
+    /// Empties `profile_name`'s stored param declarations, persisting settings — the counterpart to
+    /// `record_param_declaration` for `DELETE /api/params` (ticket 052). A profile only ever stores
+    /// manually-declared params (auto-derived ones live only in the engine, never persisted here), so
+    /// this is enough to keep the whole set from reappearing on next load; the engine-side clear
+    /// re-derives whatever auto params the retained log text still supports.
+    pub fn clear_param_declarations(
+        &mut self,
+        settings_path: &Path,
+        profile_name: &str,
+    ) -> Result<(), ProfileError> {
+        let profile = self
+            .profiles
+            .iter_mut()
+            .find(|p| p.name == profile_name)
+            .ok_or(ProfileError::NotFound)?;
+        profile.params.clear();
+        self.save(settings_path)?;
+        Ok(())
+    }
+
     /// Records/updates a declared param into `profile_name`'s stored declarations (matched by param
     /// name), persisting settings. Intended to be called by the HTTP API alongside declaring against
     /// the engine, so declarations survive a restart.