refactor: extract AppEvent to crates/ironclaw_common (#1615)

* refactor: extract AppEvent to crates/ironclaw_common

SseEvent was defined in src/channels/web/types.rs but imported by 12+
modules across agent, orchestrator, worker, tools, and extensions — it
had become the application-wide event protocol, not a web transport
concern.

Create crates/ironclaw_common as a shared workspace crate and move the
enum there as AppEvent.  Also move the truncate_preview utility which
was similarly leaked from the web gateway into agent modules.

- New crate: crates/ironclaw_common (AppEvent, truncate_preview)
- Rename SseEvent → AppEvent, from_sse_event → from_app_event
- web/types.rs re-exports AppEvent for internal gateway use
- web/util.rs re-exports truncate_preview
- Wire format unchanged (serde renames are on variants, not the enum)

Aligned with the event bus direction on refactor/architectural-hardening
where DomainEvent (≡ AppEvent) is wrapped in a SystemEvent envelope.

Co-Authored-By: Claude Opus 4.6 (1M context) <[email protected]>

* refactor: add AppEvent::event_type() helper, deduplicate match blocks

Address Gemini review: extract the variant→string match into a single
method on AppEvent, replacing the duplicated 22-arm matches in sse.rs
and types.rs.

Co-Authored-By: Claude Opus 4.6 (1M context) <[email protected]>

* refactor: rename leftover sse vars/tests to match AppEvent rename

Address Copilot review: rename sse_event vars to app_event in
orchestrator/api.rs and ws.rs, rename test functions from
test_ws_server_from_sse_* to test_ws_server_from_app_event_*, and
update stale SSE comments.

Co-Authored-By: Claude Opus 4.6 (1M context) <[email protected]>

* refactor: add Deserialize to AppEvent, round-trip test, fix stale comments

Address zmanian review:
- Add Deserialize derive to AppEvent so downstream consumers can
  deserialize incoming events
- Add event_type_matches_serde_type_field test that round-trips every
  variant through serde and asserts event_type() matches the serialized
  "type" field — catches drift between serde renames and the manual match
- Add round_trip_deserialize test for basic Serialize/Deserialize parity
- Update remaining "SSE" references in comments across server.rs,
  manager.rs, ws_gateway_integration.rs, and worker/job.rs

Co-Authored-By: Claude Opus 4.6 (1M context) <[email protected]>

---------

Co-authored-by: Claude Opus 4.6 (1M context) <[email protected]>

src/worker/job.rs

@@ -18,7 +18,6 @@ use crate::agent::agentic_loop::{
 };
 use crate::agent::scheduler::WorkerMessage;
 use crate::agent::task::TaskOutput;
-use crate::channels::web::types::SseEvent;
 use crate::context::{ContextManager, JobState};
 use crate::db::Database;
 use crate::error::Error;
@@ -33,6 +32,7 @@ use crate::tools::rate_limiter::RateLimitResult;
 use crate::tools::{
     ApprovalContext, ToolRegistry, autonomous_unavailable_error, prepare_tool_params, redact_params,
 };
+use ironclaw_common::AppEvent;
 
 /// Shared dependencies for worker execution.
 ///
@@ -48,7 +48,7 @@ pub struct WorkerDeps {
     pub hooks: Arc<HookRegistry>,
     pub timeout: Duration,
     pub use_planning: bool,
-    /// SSE manager for live job event streaming to the web gateway.
+    /// Broadcast sender for live job event streaming to the web gateway.
     pub sse_tx: Option<Arc<crate::channels::web::sse::SseManager>>,
     /// Approval context for tool execution. When `None`, all non-`Never` tools are
     /// blocked (legacy behavior). When `Some`, the context determines which tools
@@ -141,7 +141,7 @@ impl Worker {
         if let Some(ref sse) = self.deps.sse_tx {
             let job_id_str = job_id.to_string();
             let event = match event_type {
-                "message" => Some(SseEvent::JobMessage {
+                "message" => Some(AppEvent::JobMessage {
                     job_id: job_id_str,
                     role: data
                         .get("role")
@@ -154,7 +154,7 @@ impl Worker {
                         .unwrap_or("")
                         .to_string(),
                 }),
-                "tool_use" => Some(SseEvent::JobToolUse {
+                "tool_use" => Some(AppEvent::JobToolUse {
                     job_id: job_id_str,
                     tool_name: data
                         .get("tool_name")
@@ -166,7 +166,7 @@ impl Worker {
                         .cloned()
                         .unwrap_or(serde_json::Value::Null),
                 }),
-                "tool_result" => Some(SseEvent::JobToolResult {
+                "tool_result" => Some(AppEvent::JobToolResult {
                     job_id: job_id_str,
                     tool_name: data
                         .get("tool_name")
@@ -179,7 +179,7 @@ impl Worker {
                         .unwrap_or("")
                         .to_string(),
                 }),
-                "status" => Some(SseEvent::JobStatus {
+                "status" => Some(AppEvent::JobStatus {
                     job_id: job_id_str,
                     message: data
                         .get("message")
@@ -187,7 +187,7 @@ impl Worker {
                         .unwrap_or("")
                         .to_string(),
                 }),
-                "result" => Some(SseEvent::JobResult {
+                "result" => Some(AppEvent::JobResult {
                     job_id: job_id_str,
                     status: data
                         .get("status")