fix(check-types): guard tsc -b against emitting into source tree

[PaulRobson]

Follow-up to #21.

• Emit guard: when check-types uses tsc -b, it first reads every config in the reference graph (with extends applied, no file globbing; ~5 ms). If any config with inputs has no noEmit, outDir or outFile, the check fails with the offending configs and the fix, instead of tsc -b writing .js next to the source. The Vite template and composite builds into outDir pass.
• Malformed tsconfig on Windows: ts.readConfigFile threw an internal Debug Failure on backslash paths when the tsconfig had a syntax error. Paths are now forward-slashed and read errors fall back to tsc --noEmit, so tsc reports the real syntax error.
• .tsbuildinfo: tsc -b rejects --tsBuildInfoFile/--outDir on the CLI (TS5094), so it can't be suppressed. README and the guard message point to tsBuildInfoFile under node_modules/.tmp.
• Registry test covers the command being resolved per cwd at eject time.

Verification

• Scratch project with root include + references and no noEmit: verifyx check-types fails with the message and writes no files (previously wrote src/a.js).
• Tested against a client project, type check errors are found that were not found before. No new files are created outside of .gitignored directories.