fix(release): keep stable docs live during prereleases

[bokelley]

Fix the release-PR docs navigation gate so prerelease package versions do not prematurely require that release line to own the live docs tree.

Stable packages still require an exact major/minor match. Prerelease packages allow the current stable docs line, while rejecting a future docs line.

Unblocks the generated 3.2 beta release PR #5785.

Tested: node tests/docs-nav-validation.test.cjs (22/22).

[aao-secretariat]

Ladon verdict: Approve

Approve — test-only change with no blocking findings.

Checked: single-file change to tests/docs-nav-validation.test.cjs that swaps an exact major.minor package-vs-live-docs match for isLiveDocsVersionCompatible, keeping the prior stable docs line valid while a prerelease package (beta pre-mode on main) sits on the next line. The stable path is unchanged and the motivation is sound. No static/schemas/source/**, docs, dist/** artifact, or wire shape touched; no changeset required. No high-risk paths, no gated paths, no author team gate.

Only finding is a low-severity nit (prerelease branch accepts the same line as the package via <=, contradicting the accompanying comment and left untested at line 23) — not blocking.

Decision table: no critical/high findings (row 1 n/a); gated_paths false (row 2 n/a); no deletions/modifications on high-risk paths (rows 3–5 n/a); no prior decision (row 6 n/a); no team gate (row 7 n/a); fewer than three medium findings (row 8 n/a, the sole finding is low). Falls through to row 9 → approve.