fix(cli): report unsupported-language projects instead of finishing silently (#1806)

A project CodeGraph has no grammar for was indistinguishable from an empty one: unsupported extensions are filtered out at discovery, so filesDiscovered was 0, the reconciliation in index.ts found no shortfall and recorded index_state as complete, and the CLI printed the same 'No files found to index' it prints for an empty repo.

That silence is what makes it costly over MCP: an empty result reads identically to 'no match', and the agent has been told to trust the graph rather than grep.

The scan already visits every file, so the tally of what it declined to index costs no extra I/O and no second pass. index_state itself is left alone: changing its values would change the status --json contract, which is a call for the maintainer to make.


(cherry picked from commit 2c20892789897f502f84152f78b777b11d65fdaa)

Co-authored-by: Max Hsu <maxmilian@gmail.com>
Co-authored-by: netbrah <netbrah@users.noreply.github.com>

CHANGELOG.md

@@ -163,6 +163,8 @@ and adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
 
 - Files opted in with `includeIgnored` now stay indexed on Git older than 2.36, and embedded repositories remain visible to the watcher (thanks @maxmilian and @newshowardz777; #1549).
 
+- `codegraph init` and `codegraph index` now list unsupported file extensions and explain that CodeGraph is inactive when no supported source files are found (#1502).
+
 #### Screens, links and navigation
 
 - **Where the app goes after login is a fork, not two always-es.** A navigation whose destination comes back from a helper — `router.replace(await resolvePostLoginRoute())` over `return (await hasSeenWelcome(…)) ? '/home/' : '/welcome/'` — drew both screens with no condition, reading as if the welcome screen always shows. The two arms share a line, and only a column can tell them apart; each synthesized edge now carries its literal's own position, so the guard reader says which arm it is: `WHEN await hasSeenWelcome(…)` → home, and its negation → welcome. And the scan starts at the helper's body, so a literal-union return type — `Promise<'/welcome/' | '/home/'>`, whose routes are string literals too, written first — no longer stands in for the navigation itself. Re-index after upgrading to pick the positions up.