fix(harness): cp-service-token/v1 — restage ESO secret, fix unreadable-by-agent bug

The ESO-mounted secret is root-owned mode 0400 (correct — init.sh runs as
root before the gosu drop to the agent user). The original version of
this context pointed CP_SERVICE_TOKEN_FILE directly at that raw mount,
which the agent process (uid 1000) can never read.

Confirmed live 2026-09-03: a real scope-decompose-sonnet@1 dispatch
against concept 7666d278-ae58-4f12-990d-c4959a3e19a9 hit exactly this —
the agent correctly diagnosed 'cp_cli invocation can't proceed... token
is root-owned mode 0400 so it's not readable by the agent user', wrote
its decompose plan, but could never actually call cp-cli to create the
child tasks. The trigger engine's new side-effect verification (finalize.py,
bug 9dffc5b8) correctly caught this and refused to advance flow_state —
so this was a visible, retriable failure rather than another silent
false-positive.

Fix: init.sh restages the secret to /run/agent/cp-service-token/token,
mode 0600, owned by the agent user — mirrors
anthropic-cloud-paul-oauth/v1/init.sh's existing pattern.
CP_SERVICE_TOKEN_FILE now points at the restaged copy.

harnesses/contexts/cp-service-token/v1/harness.yaml

@@ -5,16 +5,23 @@ description: "CP-internal service bearer token — authenticates agent-container
 requires: []
 provides: []
 
-# AU-51b: static env pointing at the ESO-mounted secret file. No init.sh
-# needed — the mount path is fixed at harness-authoring time (unlike
-# anthropic-cloud-paul-oauth/v1, which transforms its secret into a
-# different file format and therefore needs a staging script), and
-# decompose_work_items_action reads CP_SERVICE_TOKEN_FILE directly.
+# AU-51b: the ESO-mounted secret is root-owned mode 0400 (init.sh runs as
+# root, before the gosu drop to the agent user, uid 1000) — unreadable by
+# the agent process directly. Confirmed live 2026-09-03: a real agent
+# session hit exactly this ("cp-cli invocation can't proceed... token is
+# root-owned mode 0400 so it's not readable by the agent user"). Mirrors
+# anthropic-cloud-paul-oauth/v1's pattern: init.sh restages a 0600
+# agent-owned copy outside the ESO mount. CP_SERVICE_TOKEN_FILE points at
+# the restaged copy, not the raw mount.
+#
 # The value at this path MUST match the CP's CP_INTERNAL_BEARER_TOKEN
 # (same account: cp-decompose-service-token, account_id
 # 1d963673-6ac9-4f85-875a-2ce5323e76ad, owner (cp, cp)).
 env:
-  CP_SERVICE_TOKEN_FILE: /run/agent/secrets/cp-service-token/value
+  CP_SERVICE_TOKEN_FILE: /run/agent/cp-service-token/token
+
+scripts:
+  init: "./init.sh"
 
 secrets_required:
   - name: cp-service-token

harnesses/contexts/cp-service-token/v1/init.sh

@@ -0,0 +1,39 @@
+#!/bin/bash
+# cp-service-token init — restage the ESO-mounted secret to an agent-owned
+# copy.
+#
+# Threat model: keep the ESO mount root-only (mode 0400) so the agent user
+# cannot directly `cat` /run/agent/secrets/cp-service-token/*. init.sh runs
+# as root (in uid-wrapper.sh, before the gosu drop) and writes a restaged
+# copy at /run/agent/cp-service-token/token with mode 0600 owned by the
+# agent user. This mirrors anthropic-cloud-paul-oauth/v1/init.sh's pattern.
+#
+# Bug discovered live 2026-09-03: without this restaging step, cp-cli
+# (invoked by the agent user, uid 1000) could not read the raw 0400
+# root-owned mount at all — "cp_cli invocation can't proceed... token is
+# root-owned mode 0400 so it's not readable by the agent user". The context
+# originally set CP_SERVICE_TOKEN_FILE directly at the raw ESO mount path,
+# which is the mistake this init.sh fixes.
+
+set -euo pipefail
+
+ESO_TOKEN="/run/agent/secrets/cp-service-token/value"
+
+if [ ! -r "$ESO_TOKEN" ]; then
+    echo "ERROR: $ESO_TOKEN not readable. Check ESO ExternalSecret acct-1d963673." >&2
+    exit 1
+fi
+
+AGENT_USER="${AGENT_USER:-agent}"
+
+DEST_DIR="/run/agent/cp-service-token"
+mkdir -p "$DEST_DIR"
+
+DEST_FILE="$DEST_DIR/token"
+cp "$ESO_TOKEN" "$DEST_FILE"
+
+chown "$AGENT_USER:" "$DEST_DIR" "$DEST_FILE" 2>/dev/null || true
+chmod 0700 "$DEST_DIR"
+chmod 0600 "$DEST_FILE"
+
+echo "cp-service-token: restaged into $DEST_FILE (0600 $AGENT_USER:$AGENT_USER)"