P2 BLOCKING exit green: approval interception chain end-to-end

- tc-tools: Effect declarations -> §15 GatedCategory mapping, deny-by-default
  external reach, taint invariant property-tested (tainted external effects
  are NEVER auto-allowed)
- tc-safety: pending approvals with exact payload+preview, CAS decide with
  audit + single-use grant in one tx, checkpoint suspend/load, exclusive
  resume claim, expiry sweep, decided-unresumed work queue (migration 0004
  adds the outbox the gated email.send tool writes)
- tc-runtime: resumable LoopState checkpointed to agent_runs; gated tool ->
  approval row -> approval_required/run_suspended events -> suspend; resume
  consumes the grant BEFORE executing (spent grant = no execution), rejection
  feeds a structured refusal in-band; durable resume sweeper; continuous
  journal seq across suspension (tested). ContentPart::Text became a struct
  variant — internally-tagged newtype primitives don't serialize
- tc-api: GET/decide approvals endpoints (409 double-decide, tenant
  isolation), decision triggers in-process resume; full chain proven over
  HTTP incl. gateway resumeFrom continuation
- frontend: approval_required/run_suspended events, suspended reply state,
  inline ApprovalCard (§10: summary, category, exact payload preview,
  approve/reject -> decide + stream re-attach), /approvals queue page, nav
- E2E (14 journeys, workers:1 to serialize the shared backend): gated email
  blocks with disabled composer -> approve -> continuation + ✓ step + reload
  replay; reject -> ✗ step, nothing executed; queue page decides pending

106 Rust + 61 frontend tests + 14 Playwright journeys green.

Co-Authored-By: Claude Fable 5 <[email protected]>

crates/tc-llm/src/anthropic.rs

@@ -42,7 +42,7 @@ impl AnthropicProvider {
                     .parts
                     .iter()
                     .map(|part| match part {
-                        ContentPart::Text(text) => json!({"type": "text", "text": text}),
+                        ContentPart::Text { text } => json!({"type": "text", "text": text}),
                         ContentPart::ToolUse { id, name, input } => {
                             json!({"type": "tool_use", "id": id, "name": name, "input": input})
                         }

crates/tc-llm/src/openai_compat.rs

@@ -35,7 +35,7 @@ impl OpenAiCompatProvider {
             let mut tool_calls: Vec<Value> = Vec::new();
             for part in &message.parts {
                 match part {
-                    ContentPart::Text(t) => text.push_str(t),
+                    ContentPart::Text { text: t } => text.push_str(t),
                     ContentPart::ToolUse { id, name, input } => tool_calls.push(json!({
                         "id": id,
                         "type": "function",

crates/tc-llm/src/provider.rs

@@ -15,7 +15,12 @@ pub enum ChatRole {
 #[derive(Debug, Clone, PartialEq, Serialize, Deserialize)]
 #[serde(tag = "type", rename_all = "snake_case")]
 pub enum ContentPart {
-    Text(String),
+    // Struct variant (not newtype): internally-tagged enums cannot
+    // serialize newtype primitives, and this type round-trips through
+    // `agent_runs.checkpoint`.
+    Text {
+        text: String,
+    },
     ToolUse {
         id: String,
         name: String,
@@ -27,6 +32,13 @@ pub enum ContentPart {
     },
 }
 
+impl ContentPart {
+    /// Convenience constructor for plain text parts.
+    pub fn text(value: impl Into<String>) -> ContentPart {
+        ContentPart::Text { text: value.into() }
+    }
+}
+
 #[derive(Debug, Clone, PartialEq, Serialize, Deserialize)]
 pub struct ChatMessage {
     pub role: ChatRole,

crates/tc-llm/src/scripted.rs

@@ -92,7 +92,7 @@ impl LlmProvider for ScriptedProvider {
             .iter()
             .flat_map(|m| m.parts.iter())
             .filter_map(|p| match p {
-                ContentPart::Text(t) => Some(t.as_str()),
+                ContentPart::Text { text } => Some(text.as_str()),
                 _ => None,
             })
             .collect::<Vec<_>>()
@@ -149,7 +149,7 @@ impl LlmProvider for ScriptedProvider {
                     .rev()
                     .flat_map(|m| m.parts.iter())
                     .find_map(|p| match p {
-                        ContentPart::Text(t) => Some(t.clone()),
+                        ContentPart::Text { text } => Some(text.clone()),
                         _ => None,
                     })
                     .unwrap_or_default();