Add bash mode for executing shell commands

- Add ! prefix in TUI editor to execute shell commands directly
- Output streams in real-time and is added to LLM context
- Supports multiline commands, cancellation (Escape), truncation
- Preview mode shows last 20 lines, Ctrl+O expands full output
- Commands persist in session history as bashExecution messages
- Add bash command to RPC mode via {type:'bash',command:'...'}
- Add RPC tests for bash command execution and context inclusion
- Update docs: rpc.md, session.md, README.md, CHANGELOG.md

Closes #112

Co-authored-by: Markus Ylisiurunen <markus.ylisiurunen@gmail.com>

packages/coding-agent/src/compaction.ts

@@ -8,6 +8,7 @@
 import type { AppMessage } from "@mariozechner/pi-agent-core";
 import type { AssistantMessage, Model, Usage } from "@mariozechner/pi-ai";
 import { complete } from "@mariozechner/pi-ai";
+import { messageTransformer } from "./messages.js";
 import type { CompactionEntry, SessionEntry } from "./session-manager.js";
 
 // ============================================================================
@@ -184,11 +185,14 @@ export async function generateSummary(
 		? `${SUMMARIZATION_PROMPT}\n\nAdditional focus: ${customInstructions}`
 		: SUMMARIZATION_PROMPT;
 
+	// Transform custom messages (like bashExecution) to LLM-compatible messages
+	const transformedMessages = messageTransformer(currentMessages);
+
 	const summarizationMessages = [
-		...currentMessages,
+		...transformedMessages,
 		{
 			role: "user" as const,
-			content: prompt,
+			content: [{ type: "text" as const, text: prompt }],
 			timestamp: Date.now(),
 		},
 	];