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>

package-lock.json

@@ -13,6 +13,7 @@
         "commander": "^14.0.2",
         "fast-string-width": "^3.0.2",
         "fast-wrap-ansi": "^0.2.0",
+        "ignore": "^7.0.5",
         "jsonc-parser": "^3.3.1",
         "picomatch": "^4.0.3",
         "sisteransi": "^1.0.5",
@@ -1145,6 +1146,15 @@
         "node": "^8.16.0 || ^10.6.0 || >=11.0.0"
       }
     },
+    "node_modules/ignore": {
+      "version": "7.0.5",
+      "resolved": "https://registry.npmjs.org/ignore/-/ignore-7.0.5.tgz",
+      "integrity": "sha512-Hs59xBNfUIunMFgWAbGX5cq6893IbWg4KnrjbYwX3tx0ztorVgTDA6B2sxf8ejHJ4wz8BqGUMYlnzNBer5NvGg==",
+      "license": "MIT",
+      "engines": {
+        "node": ">= 4"
+      }
+    },
     "node_modules/jsonc-parser": {
       "version": "3.3.1",
       "resolved": "https://registry.npmjs.org/jsonc-parser/-/jsonc-parser-3.3.1.tgz",