refactor(release): drop release-policy.json runtime dep and next branch

Strips the release-policy.json fallback from release-version.ts so the CLI
reads its version straight from packages/cli/package.json. dev → 0.0.0-private,
installed @kaelio/ktx → the real semver baked into the published package.json.
KtxCliPackageInfo collapses to { name, version, contextPackageName }; /health
no longer depends on version files surviving past a CI run.

Replaces the dual-branch (main + next) semantic-release model with a single-
branch model on main. rcs and stables interleave on the same branch via
{ name: 'main', prerelease: 'rc', channel: 'next' } / ['main']. Drops
@semantic-release/git and @semantic-release/changelog (nothing is committed
back to the repo on any channel) and the workflow's "Prepare next prerelease
branch" step plus the KTX_PRERELEASE_BRANCH plumbing. The git tag plus the
published npm artifact carry the version forward.

Updates docs/release.md, removes the two now-unused devDeps, regenerates
pnpm-lock.yaml. 611/611 @ktx/cli tests, 173/173 script tests, type-check,
biome, knip all clean.

.github/workflows/release.yml

@@ -69,27 +69,6 @@ jobs:
       - name: Install Python dependencies
         run: uv sync --all-packages
 
-      - name: Prepare next prerelease branch
-        if: ${{ inputs.release_kind == 'rc' }}
-        run: |
-          set -euo pipefail
-
-          source_sha="$(git rev-parse HEAD)"
-          git config user.name "github-actions[bot]"
-          git config user.email "41898282+github-actions[bot]@users.noreply.github.com"
-
-          if git ls-remote --exit-code --heads origin "${KTX_PRERELEASE_BRANCH}" >/dev/null 2>&1; then
-            git fetch origin "${KTX_PRERELEASE_BRANCH}"
-            git checkout -B "${KTX_PRERELEASE_BRANCH}" "origin/${KTX_PRERELEASE_BRANCH}"
-            git merge --no-edit "${source_sha}"
-          else
-            git checkout -B "${KTX_PRERELEASE_BRANCH}" "${source_sha}"
-          fi
-
-          git push --set-upstream origin "HEAD:${KTX_PRERELEASE_BRANCH}"
-        env:
-          KTX_PRERELEASE_BRANCH: next
-
       - name: Prepare npm package root for release verification
         run: |
           set -euo pipefail
@@ -112,36 +91,16 @@ jobs:
 
       - name: Dry-run semantic release
         if: ${{ !inputs.publish_live }}
-        run: |
-          set -euo pipefail
-
-          if [ "${KTX_RELEASE_KIND}" = "rc" ]; then
-            export GITHUB_REF="refs/heads/${KTX_PRERELEASE_BRANCH}"
-            export GITHUB_REF_NAME="${KTX_PRERELEASE_BRANCH}"
-            export GITHUB_SHA="$(git rev-parse HEAD)"
-          fi
-
-          pnpm run semantic-release:dry-run
+        run: pnpm run semantic-release:dry-run
         env:
           GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
           KTX_RELEASE_KIND: ${{ inputs.release_kind }}
-          KTX_PRERELEASE_BRANCH: next
           FORCE_RELEASE: ${{ inputs.force_release }}
 
       - name: Create semantic release
         if: ${{ inputs.publish_live }}
-        run: |
-          set -euo pipefail
-
-          if [ "${KTX_RELEASE_KIND}" = "rc" ]; then
-            export GITHUB_REF="refs/heads/${KTX_PRERELEASE_BRANCH}"
-            export GITHUB_REF_NAME="${KTX_PRERELEASE_BRANCH}"
-            export GITHUB_SHA="$(git rev-parse HEAD)"
-          fi
-
-          pnpm run semantic-release
+        run: pnpm run semantic-release
         env:
           GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
           KTX_RELEASE_KIND: ${{ inputs.release_kind }}
-          KTX_PRERELEASE_BRANCH: next
           FORCE_RELEASE: ${{ inputs.force_release }}