feat: Implement Phase 2 of SDK Worker Process

- Added background agent architecture for processing tool observations and generating session summaries.
- Created SDK Prompts Module for generating prompts for the Claude Agent SDK.
- Developed XML Parser Module for parsing observation and summary XML blocks from SDK responses.
- Implemented SDK Worker Process to handle observation processing and session management.
- Updated newHook implementation to spawn the SDK worker as a detached process with path resolution for development and production.
- Created comprehensive test suite for SDK prompts, XML parsing, and HooksDatabase integration, ensuring all tests pass.
- Documented Phase 2 implementation details, architecture validation, and success criteria in PHASE2-COMPLETE.md.

src/sdk/parser.ts

@@ -0,0 +1,132 @@
+/**
+ * XML Parser Module
+ * Parses observation and summary XML blocks from SDK responses
+ */
+
+export interface ParsedObservation {
+  type: string;
+  text: string;
+}
+
+export interface ParsedSummary {
+  request: string;
+  investigated: string;
+  learned: string;
+  completed: string;
+  next_steps: string;
+  files_read: string[];
+  files_edited: string[];
+  notes: string;
+}
+
+/**
+ * Parse observation XML blocks from SDK response
+ * Returns all observations found in the response
+ */
+export function parseObservations(text: string): ParsedObservation[] {
+  const observations: ParsedObservation[] = [];
+
+  // Match <observation>...</observation> blocks (non-greedy)
+  const observationRegex = /<observation>\s*<type>([^<]+)<\/type>\s*<text>([^<]+)<\/text>\s*<\/observation>/g;
+
+  let match;
+  while ((match = observationRegex.exec(text)) !== null) {
+    const type = match[1].trim();
+    const observationText = match[2].trim();
+
+    // Validate type
+    const validTypes = ['decision', 'bugfix', 'feature', 'refactor', 'discovery'];
+    if (!validTypes.includes(type)) {
+      console.warn(`[SDK Parser] Invalid observation type: ${type}, skipping`);
+      continue;
+    }
+
+    observations.push({
+      type,
+      text: observationText
+    });
+  }
+
+  return observations;
+}
+
+/**
+ * Parse summary XML block from SDK response
+ * Returns null if no valid summary found
+ */
+export function parseSummary(text: string): ParsedSummary | null {
+  // Match <summary>...</summary> block (non-greedy)
+  const summaryRegex = /<summary>([\s\S]*?)<\/summary>/;
+  const summaryMatch = summaryRegex.exec(text);
+
+  if (!summaryMatch) {
+    return null;
+  }
+
+  const summaryContent = summaryMatch[1];
+
+  // Extract required fields
+  const request = extractField(summaryContent, 'request');
+  const investigated = extractField(summaryContent, 'investigated');
+  const learned = extractField(summaryContent, 'learned');
+  const completed = extractField(summaryContent, 'completed');
+  const next_steps = extractField(summaryContent, 'next_steps');
+  const notes = extractField(summaryContent, 'notes');
+
+  // Extract file arrays
+  const files_read = extractFileArray(summaryContent, 'files_read');
+  const files_edited = extractFileArray(summaryContent, 'files_edited');
+
+  // Validate all required fields are present
+  if (!request || !investigated || !learned || !completed || !next_steps || !notes) {
+    console.warn('[SDK Parser] Summary missing required fields');
+    return null;
+  }
+
+  return {
+    request,
+    investigated,
+    learned,
+    completed,
+    next_steps,
+    files_read,
+    files_edited,
+    notes
+  };
+}
+
+/**
+ * Extract a simple field value from XML content
+ */
+function extractField(content: string, fieldName: string): string | null {
+  const regex = new RegExp(`<${fieldName}>([^<]*)</${fieldName}>`);
+  const match = regex.exec(content);
+  return match ? match[1].trim() : null;
+}
+
+/**
+ * Extract file array from XML content
+ * Handles both <file> children and empty tags
+ */
+function extractFileArray(content: string, arrayName: string): string[] {
+  const files: string[] = [];
+
+  // Match the array block
+  const arrayRegex = new RegExp(`<${arrayName}>(.*?)</${arrayName}>`, 's');
+  const arrayMatch = arrayRegex.exec(content);
+
+  if (!arrayMatch) {
+    return files;
+  }
+
+  const arrayContent = arrayMatch[1];
+
+  // Extract individual <file> elements
+  const fileRegex = /<file>([^<]+)<\/file>/g;
+  let fileMatch;
+  while ((fileMatch = fileRegex.exec(arrayContent)) !== null) {
+    files.push(fileMatch[1].trim());
+  }
+
+  return files;
+}