fix(install): identify generated tsconfig by sentinel, not path string
The resolver-side coupling between the generated .deno/tsconfig.json
and Deno's checker leaned on two fragile string matches:
- `.contains(".deno/tsconfig.json")` on extends targets — wouldn't fire
on Windows (where the path uses backslashes) and would also drop a
user-written file legitimately at that path.
- Stripping the literal string "deno" from `compilerOptions.types` —
invisibly clobbered the rare user who genuinely wrote that.
Tag the generated tsconfig with a top-level `_deno_generated: true`
sentinel (stock tsc/tsgo ignore unknown top-level properties). The
read path now exposes that bit, and the extends filter skips by the
flag rather than by path. The types-filter for "deno" was now dead
(generated tsconfigs no longer make it past the extends filter) so
remove it.