feat(tui): subagent spawn observability overlay

Adds a live + post-hoc audit surface for recursive delegate_task fan-out.
None of cc/oc/oclaw tackle nested subagent trees inside an Ink overlay;
this ships a view-switched dashboard that handles arbitrary depth + width.

Python
- delegate_tool: every subagent event now carries subagent_id, parent_id,
  depth, model, tool_count; subagent.complete also ships input/output/
  reasoning tokens, cost, api_calls, files_read/files_written, and a
  tail of tool-call outputs
- delegate_tool: new subagent.spawn_requested event + _active_subagents
  registry so the overlay can kill a branch by id and pause new spawns
- tui_gateway: new RPCs delegation.status, delegation.pause,
  subagent.interrupt, spawn_tree.save/list/load (disk under
  \$HERMES_HOME/spawn-trees/<session>/<ts>.json)

TUI
- /agents overlay: full-width list mode (gantt strip + row picker) and
  Enter-to-drill full-width scrollable detail mode; inverse+amber
  selection, heat-coloured branch markers, wall-clock gantt with tick
  ruler, per-branch rollups
- Detail pane: collapsible accordions (Budget, Files, Tool calls, Output,
  Progress, Summary); open-state persists across agents + mode switches
  via a shared atom
- /replay [N|last|list|load <path>] for in-memory + disk history;
  /replay-diff <a> <b> for side-by-side tree comparison
- Status-bar SpawnHud warns as depth/concurrency approaches caps;
  overlay auto-follows the just-finished turn onto history[1]
- Theme: bump DARK dim #B8860B → #CC9B1F for readable secondary text
  globally; keep LIGHT untouched

Tests: +29 new subagentTree unit tests; 215/215 passing.

ui-tui/src/app/slash/commands/ops.ts

@@ -1,6 +1,19 @@
-import type { SlashExecResponse, ToolsConfigureResponse } from '../../../gatewayTypes.js'
+import type {
+  DelegationPauseResponse,
+  SlashExecResponse,
+  SpawnTreeListResponse,
+  SpawnTreeLoadResponse,
+  ToolsConfigureResponse
+} from '../../../gatewayTypes.js'
 import type { PanelSection } from '../../../types.js'
+import { applyDelegationStatus, getDelegationState } from '../../delegationStore.js'
 import { patchOverlayState } from '../../overlayStore.js'
+import {
+  getSpawnHistory,
+  pushDiskSnapshot,
+  setDiffPair,
+  type SpawnSnapshot
+} from '../../spawnHistoryStore.js'
 import type { SlashCommand } from '../types.js'
 
 interface SkillInfo {
@@ -42,6 +55,163 @@ interface SkillsBrowseResponse {
 }
 
 export const opsCommands: SlashCommand[] = [
+  {
+    aliases: ['tasks'],
+    help: 'open the spawn-tree dashboard (live audit + kill/pause controls)',
+    name: 'agents',
+    run: (arg, ctx) => {
+      const sub = arg.trim().toLowerCase()
+
+      // Stay compatible with the gateway `/agents [pause|resume|status]` CLI —
+      // explicit subcommands skip the overlay and act directly so scripts and
+      // multi-step flows can drive it without entering interactive mode.
+      if (sub === 'pause' || sub === 'resume' || sub === 'unpause') {
+        const paused = sub === 'pause'
+        ctx.gateway.gw
+          .request<DelegationPauseResponse>('delegation.pause', { paused })
+          .then(r => {
+            applyDelegationStatus({ paused: r?.paused })
+            ctx.transcript.sys(`delegation · ${r?.paused ? 'paused' : 'resumed'}`)
+          })
+          .catch(ctx.guardedErr)
+
+        return
+      }
+
+      if (sub === 'status') {
+        const d = getDelegationState()
+        ctx.transcript.sys(
+          `delegation · ${d.paused ? 'paused' : 'active'} · caps d${d.maxSpawnDepth ?? '?'}/${d.maxConcurrentChildren ?? '?'}`
+        )
+
+        return
+      }
+
+      patchOverlayState({ agents: true, agentsInitialHistoryIndex: 0 })
+    }
+  },
+
+  {
+    help: 'replay a completed spawn tree · `/replay [N|last|list|load <path>]`',
+    name: 'replay',
+    run: (arg, ctx) => {
+      const history = getSpawnHistory()
+      const raw = arg.trim()
+      const lower = raw.toLowerCase()
+
+      // ── Disk-backed listing ─────────────────────────────────────
+      if (lower === 'list' || lower === 'ls') {
+        ctx.gateway.rpc<SpawnTreeListResponse>('spawn_tree.list', {
+          limit: 30,
+          session_id: ctx.sid ?? 'default'
+        })
+          .then(
+            ctx.guarded<SpawnTreeListResponse>(r => {
+              const entries = r.entries ?? []
+
+              if (!entries.length) {
+                return ctx.transcript.sys('no archived spawn trees on disk for this session')
+              }
+
+              const rows: [string, string][] = entries.map(e => {
+                const ts = e.finished_at ? new Date(e.finished_at * 1000).toLocaleString() : '?'
+                const label = e.label || `${e.count} subagents`
+
+                return [`${ts} · ${e.count}×`, `${label}\n  ${e.path}`]
+              })
+
+              ctx.transcript.panel('Archived spawn trees', [{ rows }])
+            })
+          )
+          .catch(ctx.guardedErr)
+
+        return
+      }
+
+      // ── Disk-backed load by path ─────────────────────────────────
+      if (lower.startsWith('load ')) {
+        const path = raw.slice(5).trim()
+
+        if (!path) {
+          return ctx.transcript.sys('usage: /replay load <path>')
+        }
+
+        ctx.gateway.rpc<SpawnTreeLoadResponse>('spawn_tree.load', { path })
+          .then(
+            ctx.guarded<SpawnTreeLoadResponse>(r => {
+              if (!r.subagents?.length) {
+                return ctx.transcript.sys('snapshot empty or unreadable')
+              }
+
+              // Push onto the in-memory history so the overlay picks it up
+              // by index 1 just like any other snapshot.
+              pushDiskSnapshot(r, path)
+              patchOverlayState({ agents: true, agentsInitialHistoryIndex: 1 })
+            })
+          )
+          .catch(ctx.guardedErr)
+
+        return
+      }
+
+      // ── In-memory nav (same-session) ─────────────────────────────
+      if (!history.length) {
+        return ctx.transcript.sys('no completed spawn trees this session · try /replay list')
+      }
+
+      let index = 1
+
+      if (raw && lower !== 'last') {
+        const parsed = parseInt(raw, 10)
+
+        if (Number.isNaN(parsed) || parsed < 1 || parsed > history.length) {
+          return ctx.transcript.sys(`replay: index out of range 1..${history.length} · use /replay list for disk`)
+        }
+
+        index = parsed
+      }
+
+      patchOverlayState({ agents: true, agentsInitialHistoryIndex: index })
+    }
+  },
+
+  {
+    help: 'diff two completed spawn trees · `/replay-diff <baseline> <candidate>` (indexes from /replay list or history N)',
+    name: 'replay-diff',
+    run: (arg, ctx) => {
+      const parts = arg.trim().split(/\s+/).filter(Boolean)
+
+      if (parts.length !== 2) {
+        return ctx.transcript.sys('usage: /replay-diff <a> <b>  (e.g. /replay-diff 1 2 for last two)')
+      }
+
+      const [a, b] = parts
+      const history = getSpawnHistory()
+
+      const resolve = (token: string): null | SpawnSnapshot => {
+        const n = parseInt(token!, 10)
+
+        if (Number.isFinite(n) && n >= 1 && n <= history.length) {
+          return history[n - 1] ?? null
+        }
+
+        return null
+      }
+
+      const baseline = resolve(a!)
+      const candidate = resolve(b!)
+
+      if (!baseline || !candidate) {
+        return ctx.transcript.sys(
+          `replay-diff: could not resolve indices · history has ${history.length} entries`
+        )
+      }
+
+      setDiffPair({ baseline, candidate })
+      patchOverlayState({ agents: true, agentsInitialHistoryIndex: 0 })
+    }
+  },
+
   {
     help: 'browse, inspect, install skills',
     name: 'skills',