Emdash source with visual editor image upload fix

Fixes:
1. media.ts: wrap placeholder generation in try-catch
2. toolbar.ts: check r.ok, display error message in popover

infra/perf-monitor/migrations/0001_add_server_timings_and_note.sql

@@ -0,0 +1,12 @@
+-- Add columns for Server-Timing capture and free-form run notes.
+--
+-- cold_server_timings stores the parsed Server-Timing header from the cold
+-- request as a JSON object keyed by timing name:
+--   { "<name>": { "dur": <number>, "desc"?: <string> } }
+-- Only the cold response is stored -- warm requests are aggregated into
+-- medians, so keeping N server-timing blobs per route makes no sense.
+--
+-- note is a free-form label, primarily for manual triggers
+-- (e.g. "pre-cold-start-fix baseline") but available for any source.
+ALTER TABLE perf_results ADD COLUMN cold_server_timings TEXT;
+ALTER TABLE perf_results ADD COLUMN note TEXT;

infra/perf-monitor/migrations/0002_add_warm_server_timings.sql

@@ -0,0 +1,14 @@
+-- Add column for the median-per-metric warm Server-Timing snapshot.
+--
+-- The original capture only stored cold Server-Timing (`cold_server_timings`).
+-- That's useful for cold-start investigation but useless for steady-state
+-- measurements -- which is what most performance work actually moves.
+--
+-- `warm_server_timings` stores the median duration per metric across all
+-- warm requests in a single probe, in the same JSON shape as
+-- `cold_server_timings`:
+--   { "<name>": { "dur": <number>, "desc"?: <string> } }
+--
+-- Null when the target site didn't emit Server-Timing on warm responses, or
+-- when no warm requests were issued.
+ALTER TABLE perf_results ADD COLUMN warm_server_timings TEXT;

infra/perf-monitor/migrations/0003_add_site.sql

@@ -0,0 +1,7 @@
+-- Tag each measurement with the demo site it came from. Existing rows all
+-- belong to the baseline blog-demo; the cache-demo site was added later.
+
+ALTER TABLE perf_results ADD COLUMN site TEXT NOT NULL DEFAULT 'blog';
+
+CREATE INDEX IF NOT EXISTS idx_perf_site_ts ON perf_results(site, timestamp);
+CREATE INDEX IF NOT EXISTS idx_perf_site_route_region_ts ON perf_results(site, route, region, timestamp);