chore(booter): complete P2P/POSIX roadmap — ctx 1.48, VFS, shell, docs

- Bump bareOsCtxApiVersion to 1.48.0; sync CHANGELOG, compatibility matrix,
  syscalls.example.json, ctx d.ts, generated ctx-client helper
- POSIX: getconf _SC_NPROCESSORS_ONLN; shell set -o pipefail + BARE_OS_PIPESTATUS;
  posix_utilities schema v2 + JSON Schema; generated dashboard refresh
- Host/subprocess: bare-subprocess then Node child_process spawn; optional
  backend on ctx.bareOsTrySpawnHostSubprocess; bin-worker WASM wall budget
- VFS: BARE_OS_VFS_SYSTEM_IMAGE_WRITE for system image writes + warm-cache
  eviction path; guest /.bare/account EACCES test; environ TOKEN redaction test
- Docs: corestore snapshot non-goal in package-bare-os-booter; PEAR-RUN links
  → docs/PEAR-RUN.md; POSIX pretest matrix in scripts/README + dev guide;
  environment appendix (PIPESTATUS, WASM_MS, system image write)
- Seeder: keep kernel/ mirror in sync after bundle + coreutils builds

Verified: npm test -w bare-os-booter, npm run pretest

docs/deployment/OTA_AND_BUNDLES.md

@@ -2,7 +2,7 @@
 
 Bare OS aligns with the **Holepunch** toolchain for shipping JavaScript as **Bare bundles** and (where applicable) **Pear**-style drives. This note ties upstream packages to operator workflows.
 
-**Also read:** [release-checklist.md](../release-checklist.md) · [documentation home](../README.md) · [PEAR-RUN.md](../../PEAR-RUN.md) for channel links.
+**Also read:** [release-checklist.md](../release-checklist.md) · [documentation home](../README.md) · [PEAR-RUN.md](../PEAR-RUN.md) for channel links.
 
 ## Upstream primitives