refactor(websearch): consolidate prompts with shared instructions + provider overrides

- Add SHARED_INSTRUCTIONS constant with 7 quality guidelines applied to ALL providers
- Refactor PROVIDER_CONFIG to use toolInstruction (provider-specific) and quirks (optional)
- Add buildPrompt() function to combine shared + provider-specific instructions
- Gemini: google_web_search tool instruction
- OpenCode: built-in capabilities instruction
- Grok: web search + X/Twitter quirk for real-time events

DRY improvement: shared guidelines now maintained in one place

lib/hooks/websearch-transformer.cjs

@@ -30,8 +30,21 @@ const { spawnSync } = require('child_process');
 // ============================================================================
 
 /**
- * Provider configurations - models and prompts for each CLI tool.
- * Edit these to customize search behavior.
+ * SHARED INSTRUCTIONS - Applied to ALL providers
+ * Edit here to change behavior across all CLI tools at once.
+ */
+const SHARED_INSTRUCTIONS = `Instructions:
+1. Search the web for current, up-to-date information
+2. Provide a comprehensive summary of the search results
+3. Include relevant URLs/sources when available
+4. Be concise but thorough - prioritize key facts
+5. Focus on factual information from reliable sources
+6. If results conflict, note the discrepancy
+7. Format output clearly with sections if the topic is complex`;
+
+/**
+ * PROVIDER-SPECIFIC CONFIG - Only tool-use differences and quirks
+ * Each provider may have unique capabilities or invocation methods.
  */
 const PROVIDER_CONFIG = {
   gemini: {
@@ -39,15 +52,11 @@ const PROVIDER_CONFIG = {
     model: 'gemini-2.5-flash',
     // Alternative free models: gemini-2.0-flash, gemini-1.5-flash
 
-    // Prompt template - {query} will be replaced with search query
-    prompt: `Search the web for: {query}
+    // Provider-specific: How to invoke web search (Gemini has google_web_search tool)
+    toolInstruction: 'Use the google_web_search tool to find current information.',
 
-Instructions:
-1. Use the google_web_search tool to find current information
-2. Provide a comprehensive summary of the search results
-3. Include relevant URLs/sources when available
-4. Be concise but thorough
-5. Focus on factual, up-to-date information`,
+    // Optional quirks (null if none)
+    quirks: null,
   },
 
   opencode: {
@@ -55,10 +64,11 @@ Instructions:
     model: 'opencode/gpt-5-nano',
     // Alternative models: opencode/gpt-4o, opencode/claude-3.5-sonnet
 
-    // Prompt template
-    prompt: `Search the web for: {query}
+    // Provider-specific: OpenCode has built-in web search via Zen
+    toolInstruction: 'Search the web using your built-in capabilities.',
 
-Provide a comprehensive summary with relevant URLs/sources.`,
+    // Optional quirks
+    quirks: null,
   },
 
   grok: {
@@ -66,13 +76,35 @@ Provide a comprehensive summary with relevant URLs/sources.`,
     model: 'grok-3',
     // Note: Grok CLI doesn't support model selection via CLI
 
-    // Prompt template
-    prompt: `Search the web for: {query}
+    // Provider-specific: Grok has web + X/Twitter search
+    toolInstruction: 'Use your web search capabilities to find information.',
 
-Provide a comprehensive summary with relevant URLs/sources.`,
+    // Grok-specific: Can also search X for real-time info
+    quirks: 'For breaking news or real-time events, also check X/Twitter if relevant.',
   },
 };
 
+/**
+ * Build the complete prompt for a provider
+ * Combines: query + tool instruction + shared instructions + quirks
+ */
+function buildPrompt(providerId, query) {
+  const config = PROVIDER_CONFIG[providerId];
+  const parts = [
+    `Search the web for: ${query}`,
+    '',
+    config.toolInstruction,
+    '',
+    SHARED_INSTRUCTIONS,
+  ];
+
+  if (config.quirks) {
+    parts.push('', `Note: ${config.quirks}`);
+  }
+
+  return parts.join('\n');
+}
+
 // Minimum response length to consider valid
 const MIN_VALID_RESPONSE_LENGTH = 20;
 
@@ -224,7 +256,7 @@ function tryGeminiSearch(query, timeoutSec = DEFAULT_TIMEOUT_SEC) {
   try {
     const timeoutMs = timeoutSec * 1000;
     const config = PROVIDER_CONFIG.gemini;
-    const prompt = config.prompt.replace('{query}', query);
+    const prompt = buildPrompt('gemini', query);
 
     if (process.env.CCS_DEBUG) {
       console.error(`[CCS Hook] Executing: gemini --model ${config.model} --yolo -p "..."`);
@@ -290,7 +322,7 @@ function tryOpenCodeSearch(query, timeoutSec = DEFAULT_TIMEOUT_SEC) {
 
     // Allow model override via env var
     const model = process.env.CCS_WEBSEARCH_OPENCODE_MODEL || config.model;
-    const prompt = config.prompt.replace('{query}', query);
+    const prompt = buildPrompt('opencode', query);
 
     if (process.env.CCS_DEBUG) {
       console.error(`[CCS Hook] Executing: opencode run --model ${model} "..."`);
@@ -352,8 +384,7 @@ function tryOpenCodeSearch(query, timeoutSec = DEFAULT_TIMEOUT_SEC) {
 function tryGrokSearch(query, timeoutSec = DEFAULT_TIMEOUT_SEC) {
   try {
     const timeoutMs = timeoutSec * 1000;
-    const config = PROVIDER_CONFIG.grok;
-    const prompt = config.prompt.replace('{query}', query);
+    const prompt = buildPrompt('grok', query);
 
     if (process.env.CCS_DEBUG) {
       console.error('[CCS Hook] Executing: grok "..."');