docs(powershell-lsp): refresh ROADMAP to v1.23.1 ground truth (000115)

[manderse21]

Refresh ROADMAP-powershell-lsp.md to v1.23.1 ground truth (dispatch 000115)

Doc-only, no version bump. Rewrites the stale 2026-07-01 / v1.21.1 snapshot in place to current
ground truth, verified against disk + live GitHub this session. Preserves the canonical section
structure; the retired Phase 1-4 framing is NOT reintroduced.

What changed (one file)

• ROADMAP-powershell-lsp.md -- status stamp -> v1.23.1 / 2026-07-05; recent-arc table extended
  to cover the full v1.22.0 -> v1.23.1 arc; the native-LSP story rewritten so native serve is now
  un-gated by the shipped nativeServe shim (v1.23.0), with the honest #1359 (serve handshake) and
  #73961 (Windows launcher guard) boundaries; native navigation, formatOnEdit=apply, and the AI-era
  rule pack reclassified as SHIPPED (not horizon); the remaining horizon re-derived honestly.

Reclassified out of the horizon (all shipped since the snapshot)

• Native navigation -- opt-in via the nativeServe shim (v1.23.0 / 000103).
• Format apply-mode -- the guarded formatOnEdit=apply write-back (v1.23.0 / 000099).
• AI-era rule pack -- CLOSED (v1.22.0 / 000097): slices 1-3 shipped; slice 5 + the
  Compatible-Cmdlet / Compatible-Type checks deferred by design on high false-positive rates.

Verified against disk this session

• Released version v1.23.1: git describe --tags, both manifests, the latest CHANGELOG heading;
  annotated tag gitsign-signed (cut by github-actions[bot]) at commit 20e14d7 (release: v1.23.1 -- lockstep manifest bump + CHANGELOG #78); GitHub Release
  published Latest (2026-07-04).
• Upstream re-checked live (two on-disk notes had gone stale): #1359 / #66987 / #73961 OPEN; the PSES
  rename fix (issue #2297) submitted as PR #2299 and now CLOSED unmerged (2026-06-11).
• Live dispatch list; 000054 (benchmark) and 000095 (old launch draft) abandoned; launch posts live
  • launch-draft PR docs: rewrite r/PowerShell launch draft to v1.23.0 ground truth (000112) #77 merged (per the dispatch's 2026-07-05 ground-truth addendum).
• ASCII-only, LF, no-BOM; single-file diff.

Dispatch: strategic-dispatch/powershell-lsp/000115. Merge held for Mike.

https://claude.ai/code/session_018H9bZN9qPjd6opLzc2dnGK