fix(acp): wake agents from workflow messages (#6953)

> Pinky, an AI agent, is opening this PR on Wes's behalf.

## Summary

Workflow-generated messages can contain a valid agent mention but still
fail the ACP inbound author gate because the relay signs the event. This
keeps the existing wake policy and gives ACP a narrowly verified
effective author:

- preserve the workflow owner's existing `p` tag and all
rendered-mention `p` tags
- add explicit `["buzz:workflow-owner", <owner hex>]` provenance to
relay-generated workflow messages
- add `["buzz:workflow-mention", <agent hex>]` authority only for
mentions resolved from the stored, unrendered workflow step template
- accept that owner only for a verified kind-9 event signed by the
relay's current NIP-11 `self` key, with unique canonical workflow
metadata and an explicit workflow mention for the receiving agent
- route the verified owner through the existing author and in-flight
mode policies in both normal and setup listeners
- refresh relay identity after reconnects, retaining the last verified
key on transient fetch errors while treating a successful response
without `self` as definitive removal

Malformed, duplicate, forged, tampered, wrong-kind, and wrong-relay
attribution all fail closed to the raw event signer. `respond-to=nobody`
remains absolute. Old/mixed-version messages without the explicit
provenance retain their current fail-closed behavior.

## Trust boundary

The workflow owner means **“scheduled by,” not “authored every rendered
word.”** Trigger-controlled substitutions may still produce ordinary `p`
mention routing for compatibility, but they cannot mint
`buzz:workflow-mention` authority. Only a target named in the durable
owner-authored step template can receive that authority.

The author gate is not bypassed: after relay signature/provenance
verification, the effective owner is evaluated under the same
`owner-only`, `allowlist`, DM, and `nobody` policies used for ordinary
messages. Owner control commands continue to use the raw event signer.

## Why this PR

This is the focused immediate fix for waking an **online** agent from a
stored workflow mention. Earlier attempts were not a finished mergeable
fix and had materially different or incomplete trust designs. Larry's
larger draft stack addresses durable delivery across restarts; that
remains valuable future work and can supersede this effective-author
path when it lands.

## Validation

At exact clean commit `fe5b55619fe44176343eefb4cb7fe180df45a7d8`:

- `buzz-relay workflow_sink`: 25/25 passed, including all four ignored
PostgreSQL cases
- `buzz-acp --lib`: 845/845 passed
- `buzz-workflow --lib`: 169/169 passed (2 unrelated PostgreSQL tests
ignored)
- warnings-denied Clippy passed for the changed Rust packages
- `cargo fmt --all -- --check` passed
- `git diff --check` passed
- repository pre-push gates passed, including branch-scoped Rust tests
- CI now selects the ACP library tests and the relay's pure + PostgreSQL
workflow-sink tests so these guards cannot silently remain unexecuted

The production event-to-author gate is shared by normal and setup
listeners and has biting regression tests for accepted explicit
attribution, legacy owner-`p` rejection, and forged-attribution
rejection.

## Exact-head local relay + ACP proof

Following the release-binary/local-relay shape in `TESTING.md`, the
exact commit above passed a fresh isolated real-process matrix using:

- a freshly recreated Postgres database with migrations
- isolated Redis
- exact-head release `buzz-relay`, `buzz`, `buzz-admin`, and `buzz-acp`
binaries
- newly provisioned owner, channel, and bot member through the CLI
- workflow creation and triggering through the running relay
- a deterministic ACP protocol subprocess capturing actual
`session/prompt` dispatches
- a NIP-11 `self` value verified against the running relay signer

Cases:

1. A stored explicit workflow mention woke an `owner-only` agent exactly
once.
2. A workflow message without an agent mention did not wake it.
3. A non-relay signer forging every workflow authority tag did not wake
it.
4. Trigger-controlled `{{trigger.text}}` containing `@Wake Agent`
retained ordinary `p` routing but received no authority-bearing
workflow-mention tag and did not wake the agent.
5. `respond-to=nobody` remained absolute for a valid relay-authenticated
workflow mention.

The deterministic ACP subprocess isolates and directly proves relay →
ACP authorization and prompt dispatch without depending on external
model behavior.

## Deployment and residual risk

Relay and ACP changes must be deployed together for the new wake
behavior; mixed versions fail closed. Production paired-deployment proof
remains distinct from the successful local integration run. Setup-mode
behavior has automated coverage but was not a separate case in the
five-case local matrix. Relay-key rotation is observed at ACP
startup/reconnect; transient NIP-11 errors retain the last verified key,
an intentional availability tradeoff documented in code.

---------

Signed-off-by: Pinky <5f5ab050ec58ae208332edd544ebf705221e24c1b86d82a6ca07038a7a8f6ac9@buzz.block.builderlab.xyz>
Signed-off-by: Brain <1a02c72794dcd0f07058a353bc3a81f4028b8c77c92c87fce6d5c8b85970a20b@buzz.block.builderlab.xyz>
Signed-off-by: Wes <wesbillman@users.noreply.github.com>
Co-authored-by: Pinky <5f5ab050ec58ae208332edd544ebf705221e24c1b86d82a6ca07038a7a8f6ac9@buzz.block.builderlab.xyz>
Co-authored-by: LioLionel <62820906+LioLionel@users.noreply.github.com>
Co-authored-by: Brain <1a02c72794dcd0f07058a353bc3a81f4028b8c77c92c87fce6d5c8b85970a20b@buzz.block.builderlab.xyz>
Co-authored-by: Carl <9d00794d3df50972eb8b615511783cab12a77a8fd5dd5edd58073ec73b54bd8b@buzz.block.builderlab.xyz>

.github/workflows/ci.yml

@@ -685,6 +685,18 @@ jobs:
           VALUES ('00000000-0000-4000-8000-00000000c0de', 'localhost:3000')
           ON CONFLICT (lower(host)) DO NOTHING
           ;"
+      - name: Workflow message provenance tests
+        # The relay's workflow_sink suite is not selected by the infra-free
+        # unit job. Run both its pure tests and ignored PostgreSQL tests here so
+        # authored-template provenance cannot regress behind a green CI build.
+        run: |
+          cargo nextest run \
+            --archive-file target/ci/backend-integration-tests.tar.zst \
+            -E 'package(buzz-relay) and test(/workflow_sink/)' \
+            --run-ignored all
+        env:
+          DATABASE_URL: postgres://buzz:${{ env.BUZZ_TEST_POSTGRES_PASSWORD }}@localhost:5432/buzz
+          TEST_DATABASE_URL: postgres://buzz:${{ env.BUZZ_TEST_POSTGRES_PASSWORD }}@localhost:5432/buzz
       - name: Replaceable persistence PostgreSQL tests
         # Transaction, concurrency, and mention-index coverage for the
         # replaceable-event store seam. These tests require real Postgres and