dashboard: add per-agent ctx-window usage chip to container rows

Reads the most recent turn's context-window token count directly from
each agent's hyperhive-turn-stats.sqlite (same path the host-side
stats_vacuum uses). Adds ctx_tokens: Option<u64> to ContainerView;
populated in build_all via a single best-effort SQL query.

Dashboard app.js renders a 'ctx·Nk' badge colour-coded by harness
watermarks: green <100k (safe), yellow 100-150k (near auto-reset),
red ≥150k (compact territory). Badge only shown when ctx_tokens
is present (agent has run at least one turn).

Closes #17

hive-c0re/assets/app.js

@@ -550,6 +550,21 @@
           },
           `⏰ ${c.pending_reminders}`));
       }
+      if (c.ctx_tokens != null) {
+        // Colour thresholds mirror the harness compaction watermarks:
+        // < 100k = safe (green), 100k–150k = approaching reset (yellow),
+        // ≥ 150k = compact territory (red).
+        const k = Math.round(c.ctx_tokens / 1000);
+        const ctxClass = c.ctx_tokens >= 150_000 ? 'badge-ctx-warn'
+          : c.ctx_tokens >= 100_000 ? 'badge-ctx-caution'
+          : 'badge-ctx-ok';
+        head.append(el('span',
+          {
+            class: `badge ${ctxClass}`,
+            title: `last turn context size: ${c.ctx_tokens.toLocaleString()} tokens`,
+          },
+          `ctx·${k}k`));
+      }
       li.append(head);
 
       // ── line 2: action buttons ───────────────────────────────────

hive-c0re/assets/dashboard.css

@@ -123,6 +123,20 @@ a:hover {
   color: var(--cyan); border-color: var(--cyan);
   text-shadow: 0 0 6px rgba(137, 220, 235, 0.4);
 }
+/* Context-window usage badges on dashboard container rows.
+   Green < 100k, yellow 100–150k, red ≥ 150k (mirrors harness watermarks). */
+.badge-ctx-ok {
+  color: var(--green); border-color: var(--green);
+  opacity: 0.85;
+}
+.badge-ctx-caution {
+  color: var(--amber); border-color: var(--amber);
+  text-shadow: 0 0 6px rgba(250, 179, 135, 0.5);
+}
+.badge-ctx-warn {
+  color: var(--red); border-color: var(--red);
+  text-shadow: 0 0 6px rgba(243, 139, 168, 0.5);
+}
 .container-row.tombstone {
   border-style: dashed;
   background: rgba(24, 24, 37, 0.35);

hive-c0re/src/container_view.rs

@@ -8,6 +8,7 @@
 use std::collections::HashMap;
 use std::path::Path;
 
+use rusqlite::Connection;
 use serde::Serialize;
 
 use crate::coordinator::Coordinator;
@@ -36,6 +37,13 @@ pub struct ContainerView {
     /// not real-time on remind/cancel-reminder but close enough.
     #[serde(default)]
     pub pending_reminders: u64,
+    /// Context-window size (prompt tokens) from the agent's most recent
+    /// completed turn, read directly from the turn-stats SQLite.
+    /// `None` when the file is absent or the agent has no turns yet.
+    /// Stale by up to one crash-watch cycle (~10s); good enough for
+    /// the "which agent is close to the window?" dashboard glance.
+    #[serde(default, skip_serializing_if = "Option::is_none")]
+    pub ctx_tokens: Option<u64>,
 }
 
 /// Build the full container list. Wraps `lifecycle::list()` and
@@ -74,6 +82,7 @@ pub async fn build_all(coord: &Coordinator) -> Vec<ContainerView> {
             .broker
             .count_pending_reminders_for(reminder_recipient)
             .unwrap_or(0);
+        let ctx_tokens = read_last_ctx_tokens(&logical);
         out.push(ContainerView {
             port: lifecycle::agent_web_port(&logical),
             running: lifecycle::is_running(&logical).await,
@@ -84,6 +93,7 @@ pub async fn build_all(coord: &Coordinator) -> Vec<ContainerView> {
             needs_login,
             deployed_sha,
             pending_reminders,
+            ctx_tokens,
         });
     }
     out
@@ -102,6 +112,32 @@ pub fn claude_has_session(dir: &Path) -> bool {
         .any(|e| e.file_type().is_ok_and(|t| t.is_file()))
 }
 
+/// Read the most recent completed turn's context-window size (prompt
+/// tokens) from the agent's turn-stats SQLite. Returns `None` when
+/// the file is absent or has no rows. Best-effort — any DB error
+/// silently yields `None` so a missing/corrupt file never blocks
+/// `build_all`.
+///
+/// Context tokens = `last_input_tokens + last_cache_read_input_tokens
+/// + last_cache_creation_input_tokens`, mirroring
+/// `hive_ag3nt::events::TokenUsage::context_tokens`.
+fn read_last_ctx_tokens(name: &str) -> Option<u64> {
+    let path = Coordinator::agent_notes_dir(name).join("hyperhive-turn-stats.sqlite");
+    let conn = Connection::open_with_flags(
+        &path,
+        rusqlite::OpenFlags::SQLITE_OPEN_READ_ONLY,
+    )
+    .ok()?;
+    conn.query_row(
+        "SELECT last_input_tokens + last_cache_read_input_tokens + last_cache_creation_input_tokens \
+         FROM turn_stats ORDER BY started_at DESC LIMIT 1",
+        [],
+        |row| row.get::<_, i64>(0),
+    )
+    .ok()
+    .and_then(|v| u64::try_from(v).ok())
+}
+
 /// Map of `agent-<n>` → locked sha from meta's flake.lock. Used to
 /// render the `deployed:<sha12>` chip per container row.
 fn read_meta_locked_revs() -> HashMap<String, String> {