Add generic host-verified /webhook/tools/{tool} ingress (#757)

* Add generic host-verified webhook ingress for tools

* Stabilize trace E2E test rig and approval behavior

* Fix webhook security issues from review feedback

- Reject tools without webhook_capability() (was unauthenticated RCE)
- Remove secret-in-query-string fallback (leak via logs/referrers)
- Require approval for event_emit tool (escalation via routine triggers)
- Simplify header_value() (HeaderMap already case-insensitive)
- Redact internal errors from webhook HTTP responses
- Remove unused hmac_timestamp_tolerance_secs field
- Add regression test for tool without webhook capability

[skip-regression-check]

Co-Authored-By: Claude Opus 4.6 <[email protected]>

* Harden webhook ingress: require auth mechanism, body limit layer, health check

- Reject webhook capabilities that declare no auth mechanism (empty
  WebhookCapability would previously allow unauthenticated access)
- Add DefaultBodyLimit layer to reject oversized payloads before buffering
- Health check (GET) now verifies tool has webhook_capability(), not just
  existence
- Add regression tests for all three fixes

[skip-regression-check]

Co-Authored-By: Claude Opus 4.6 <[email protected]>

* Fix auto_approve_tools inconsistency between dispatcher and thread_ops

dispatcher.rs skips all approval checks (including Always) when
auto_approve_tools is true, but thread_ops.rs still required approval
for Always tools. This caused deferred tool calls to unexpectedly halt
in test rigs and auto-approve configurations.

Match dispatcher behavior: short-circuit all approval when
auto_approve_tools is enabled.

[skip-regression-check]

Co-Authored-By: Claude Opus 4.6 <[email protected]>

---------

Co-authored-by: Claude Opus 4.6 <[email protected]>

FEATURE_PARITY.md

@@ -440,6 +440,7 @@ This document tracks feature parity between IronClaw (Rust implementation) and O
 | `before_agent_start` hook | ✅ | ❌ | P2 | Model/provider override |
 | `before_message_write` hook | ✅ | ❌ | P2 | Pre-write interception |
 | `onMessage` hook | ✅ | ✅ | - | Routines with event trigger |
+| Structured system-event routines | ✅ | ✅ | P2 | `system_event` trigger + `event_emit` tool for event-driven automation |
 | `onSessionStart` hook | ✅ | ✅ | P2 | |
 | `onSessionEnd` hook | ✅ | ✅ | P2 | |
 | `transcribeAudio` hook | ✅ | ❌ | P3 | |
@@ -558,7 +559,7 @@ This document tracks feature parity between IronClaw (Rust implementation) and O
 - ❌ Media handling (images, PDFs)
 - ✅ Ollama/local model support (via rig::providers::ollama)
 - ❌ Configuration hot-reload
-- ❌ Webhook trigger endpoint in web gateway
+- ✅ Tool-driven webhook ingress (`/webhook/tools/{tool}` -> host-verified + tool-normalized `system_event` routines)
 - ❌ Channel health monitor with auto-restart
 - ❌ Partial output preservation on abort