Merge resolve: add prompt_builder, compact_summary support, and caching config

Resolves merge conflicts integrating compact_summary parameter into
build_converse_request alongside the existing CachingConfig approach.
Adds the new prompt_builder module for structured prompt construction.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

app/src/ai/bedrock/client.rs

@@ -133,6 +133,7 @@ impl BedrockClient {
         needs_create_task: bool,
         messages: Vec<ConversationMessage>,
         system_prompt: Option<String>,
+        compact_summary: Option<String>,
         tools: Vec<ToolDefinition>,
         max_tokens: i32,
         temperature: Option<f32>,
@@ -165,6 +166,7 @@ impl BedrockClient {
         let converted = build_converse_request(
             messages.clone(),
             system_prompt.clone(),
+            compact_summary,
             tools.clone(),
             max_tokens,
             temperature,