Add QMD_CONFIG_DIR environment variable for test isolation

Collections module now supports QMD_CONFIG_DIR environment variable
to override the default config directory (~/.config/qmd). This allows
tests to use isolated YAML config files without affecting the user's
actual configuration.

All CONFIG_PATH and CONFIG_DIR references now use dynamic functions
that check the environment variable.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

.beads/issues.jsonl

@@ -33,5 +33,5 @@
 {"id":"qmd-vro","title":"Update 'qmd get' to support virtual paths","description":"Allow qmd get to accept both virtual paths (qmd://journals/...) and filesystem paths, plus fuzzy matching by filename.","status":"closed","priority":0,"issue_type":"task","created_at":"2025-12-12T15:29:53.963113-05:00","updated_at":"2025-12-12T15:47:29.178955-05:00","closed_at":"2025-12-12T15:47:29.178955-05:00","dependencies":[{"issue_id":"qmd-vro","depends_on_id":"qmd-ama","type":"discovered-from","created_at":"2025-12-12T15:29:53.963641-05:00","created_by":"daemon"}]}
 {"id":"qmd-x19","title":"Update 'qmd add-context' for collection-scoped contexts","description":"Update add-context to work with collections:\n- qmd add-context \u003ccollection\u003e/\u003cpath\u003e \"context description\"\n- Support both virtual and filesystem paths\n- Update to use new path_contexts schema","status":"closed","priority":2,"issue_type":"task","created_at":"2025-12-12T15:29:38.142575-05:00","updated_at":"2025-12-12T15:53:00.525001-05:00","closed_at":"2025-12-12T15:53:00.525001-05:00"}
 {"id":"qmd-x64","title":"for each collection, on update, check if there is a .git directory, if so write out the git status, add --pull as a qmd update --pull parameter which also executes git pull before reindexing\n","description":"","status":"closed","priority":2,"issue_type":"task","created_at":"2025-12-12T17:04:15.994054-05:00","updated_at":"2025-12-12T17:14:40.107181-05:00","closed_at":"2025-12-12T17:14:40.107181-05:00"}
-{"id":"qmd-yzj","title":"Add optional update: command support to collections YAML","description":"Collections can now specify an optional 'update:' key with a bash command that will be executed during 'qmd update' before indexing files. Runs in cwd, prints output, stops on error.","status":"open","priority":2,"issue_type":"feature","created_at":"2025-12-13T11:16:32.527608-05:00","updated_at":"2025-12-13T11:16:32.527608-05:00"}
+{"id":"qmd-yzj","title":"Add optional update: command support to collections YAML","description":"Collections can now specify an optional 'update:' key with a bash command that will be executed during 'qmd update' before indexing files. Runs in cwd, prints output, stops on error.","status":"closed","priority":2,"issue_type":"feature","created_at":"2025-12-13T11:16:32.527608-05:00","updated_at":"2025-12-13T11:17:57.500434-05:00","closed_at":"2025-12-13T11:17:57.500434-05:00"}
 {"id":"qmd-zin","title":"Improve qmd ls command to be more like ls -l with colors","description":"Make qmd ls more Unix-like:\n1. Format like ls -l with columns (permissions, size, date, name)\n2. Add colors (directories, files, etc.)\n3. Dim the qmd:// prefix to show it's optional\n4. Show file sizes in human-readable format\n5. Show modification times\n6. Consider adding -l flag for long format","status":"closed","priority":1,"issue_type":"task","created_at":"2025-12-13T09:44:48.703843-05:00","updated_at":"2025-12-13T09:48:22.298822-05:00","closed_at":"2025-12-13T09:48:22.298822-05:00"}

src/collections.ts

@@ -66,8 +66,9 @@ function getConfigFilePath(): string {
  * Ensure config directory exists
  */
 function ensureConfigDir(): void {
-  if (!existsSync(CONFIG_DIR)) {
-    mkdirSync(CONFIG_DIR, { recursive: true });
+  const configDir = getConfigDir();
+  if (!existsSync(configDir)) {
+    mkdirSync(configDir, { recursive: true });
   }
 }
 
@@ -80,12 +81,13 @@ function ensureConfigDir(): void {
  * Returns empty config if file doesn't exist
  */
 export function loadConfig(): CollectionConfig {
-  if (!existsSync(CONFIG_PATH)) {
+  const configPath = getConfigFilePath();
+  if (!existsSync(configPath)) {
     return { collections: {} };
   }
 
   try {
-    const content = readFileSync(CONFIG_PATH, "utf-8");
+    const content = readFileSync(configPath, "utf-8");
     const config = YAML.parse(content) as CollectionConfig;
 
     // Ensure collections object exists
@@ -95,7 +97,7 @@ export function loadConfig(): CollectionConfig {
 
     return config;
   } catch (error) {
-    throw new Error(`Failed to parse ${CONFIG_PATH}: ${error}`);
+    throw new Error(`Failed to parse ${configPath}: ${error}`);
   }
 }
 
@@ -104,15 +106,16 @@ export function loadConfig(): CollectionConfig {
  */
 export function saveConfig(config: CollectionConfig): void {
   ensureConfigDir();
+  const configPath = getConfigFilePath();
 
   try {
     const yaml = YAML.stringify(config, {
       indent: 2,
       lineWidth: 0,  // Don't wrap lines
     });
-    writeFileSync(CONFIG_PATH, yaml, "utf-8");
+    writeFileSync(configPath, yaml, "utf-8");
   } catch (error) {
-    throw new Error(`Failed to write ${CONFIG_PATH}: ${error}`);
+    throw new Error(`Failed to write ${configPath}: ${error}`);
   }
 }
 
@@ -356,14 +359,14 @@ export function findContextForPath(
  * Get the config file path (useful for error messages)
  */
 export function getConfigPath(): string {
-  return CONFIG_PATH;
+  return getConfigFilePath();
 }
 
 /**
  * Check if config file exists
  */
 export function configExists(): boolean {
-  return existsSync(CONFIG_PATH);
+  return existsSync(getConfigFilePath());
 }
 
 /**