v0.3.20

ts: compose Express sub-router mounts across files (#232)

A router declared in routes/*.js and mounted in index.js cannot be resolved by a
per-file pass, so its routes were dropped rather than emitted at a fragment path -
silence on the layout most Express services use. A repo-wide fixpoint now propagates
mount prefixes from the app roots, the same shape as Go v125 and Axum v130; a
non-literal prefix, an external module or an unmounted router still emits nothing, so
the pass can correct a path but never invent one.

Same pass fixes a same-file mount onto an unmounted parent, which was emitting that
fragment, and an extensioned './x.js' specifier, which resolved to nothing.

Also: `install`/`uninstall` printed the full plan twice, since --yes leaves no prompt
between the preview and the result. The second one collapses to a line unless it
diverges.

cacheVersion v198 - cached TypeScript snapshots must re-extract.