feat: zero-config indexing driven by .gitignore (#283) (#285)

Remove .codegraph/config.json and the entire config surface. CodeGraph now
indexes every file whose extension maps to a supported language and respects
.gitignore everywhere — git repos via git itself, non-git projects via the
`ignore` library (root + nested .gitignore files, the same way git does).

- Remove CodeGraphConfig/DEFAULT_CONFIG, src/config.ts, and the public config
  API (the `config` option on init, getConfig/updateConfig/getConfigPath).
- Derive the source-file allowlist from EXTENSION_MAP (isSourceFile); maxFileSize
  is now a constant. Drop the .codegraphignore marker.
- Behavior change: committed, non-gitignored dirs (vendor/, a committed dist/)
  are now indexed — .gitignore is the single source of truth.

Earlier inert fields (languages, frameworks, extractDocstrings, trackCallSites,
customPatterns) and their dead helpers are removed as part of this.

Resolves #283.

Co-authored-by: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

src/sync/watcher.ts

@@ -9,8 +9,7 @@
  */
 
 import * as fs from 'fs';
-import { CodeGraphConfig } from '../types';
-import { shouldIncludeFile } from '../extraction';
+import { isSourceFile } from '../extraction';
 import { logDebug, logWarn } from '../errors';
 import { normalizePath } from '../utils';
 import { watchDisabledReason } from './watch-policy';
@@ -44,7 +43,7 @@ export interface WatchOptions {
  * Design goals:
  * - Minimal resource usage (native OS file events, no polling)
  * - Debounced to avoid thrashing on rapid saves
- * - Filters against CodeGraph include/exclude patterns
+ * - Filters to supported source files by extension
  * - Ignores .codegraph/ directory changes
  */
 export class FileWatcher {
@@ -55,7 +54,6 @@ export class FileWatcher {
   private stopped = false;
 
   private readonly projectRoot: string;
-  private readonly config: CodeGraphConfig;
   private readonly debounceMs: number;
   private readonly syncFn: () => Promise<{ filesChanged: number; durationMs: number }>;
   private readonly onSyncComplete?: WatchOptions['onSyncComplete'];
@@ -63,12 +61,10 @@ export class FileWatcher {
 
   constructor(
     projectRoot: string,
-    config: CodeGraphConfig,
     syncFn: () => Promise<{ filesChanged: number; durationMs: number }>,
     options: WatchOptions = {}
   ) {
     this.projectRoot = projectRoot;
-    this.config = config;
     this.syncFn = syncFn;
     this.debounceMs = options.debounceMs ?? 2000;
     this.onSyncComplete = options.onSyncComplete;
@@ -112,8 +108,8 @@ export class FileWatcher {
             return;
           }
 
-          // Filter against include/exclude patterns
-          if (!shouldIncludeFile(normalized, this.config)) {
+          // Only sync changes to files we can actually parse.
+          if (!isSourceFile(normalized)) {
             return;
           }