Add profile (preset) CRUD and startup replay (ticket 009)

Introduces `src/profile.rs`: a `Profile` bundles param/metric declarations
plus a placeholder dashboards field, and `ProfileStore` persists all
profiles as a single profiles.json file, resolved relative to the settings
file's directory (same convention as ticket 010's CSS storage). Adds CRUD
(create/list/get/delete/set_active) that keeps Settings.profiles.names and
active_profile in sync, plus record_param_declaration/record_metric_declaration
hooks that ticket 004's HTTP API will call to persist newly-declared
params/metrics into the active profile.

Wires main.rs to replay the active profile's declarations into the engine
before spawning the ingest task, so backfill/live-derivation semantics
apply uniformly to every ingested line.

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

src/main.rs

@@ -7,6 +7,7 @@ mod filter_parser;
 mod index_key;
 mod ingest;
 mod metric_primitive;
+mod profile;
 mod settings;
 mod timestamp;
 
@@ -17,6 +18,7 @@ use clap::Parser;
 use tokio::net::TcpListener;
 use tokio::sync::mpsc;
 
+use profile::ProfileStore;
 use settings::Settings;
 
 /// Observability dashboard from terminal output.
@@ -48,6 +50,38 @@ async fn main() {
 
     let (engine_tx, engine_rx) = mpsc::channel(1024);
     tokio::spawn(engine::run(engine_rx));
+
+    // Ticket 009: reload the active profile's param/metric declarations into the
+    // engine BEFORE starting ingest below. Ordering matters: declarations must be
+    // in place before any line is ingested so that backfill/live-derivation
+    // semantics (ticket 003) apply uniformly to every line, including ones that
+    // arrive immediately once ingest starts (there's no "declare after the fact
+    // and go back to reprocess early lines" step, so doing it after ingest starts
+    // could silently miss lines that raced ahead of the declarations).
+    {
+        let (active_profile_name, profiles_dir) = {
+            let settings_guard = settings.lock().unwrap();
+            (
+                settings_guard.profiles.active_profile.clone(),
+                profile::resolve_profiles_dir(&settings_guard, &settings_path),
+            )
+        };
+        if let Some(profile_name) = active_profile_name {
+            let store = ProfileStore::load(&profile::profiles_store_path(&profiles_dir));
+            match store.get(&profile_name) {
+                Some(active_profile) => {
+                    profile::load_into_engine(&engine_tx, active_profile).await;
+                }
+                None => {
+                    eprintln!(
+                        "warning: active profile '{profile_name}' not found under {}; skipping",
+                        profiles_dir.display()
+                    );
+                }
+            }
+        }
+    }
+
     tokio::spawn(ingest::run(engine_tx.clone()));
 
     let app = api::router(engine_tx, &args.static_dir, settings, settings_path);