fix(readme): remove unreleased candidate messaging

[AgentArcLab]

Removes the unreleased 0.8 review-candidate section from all public README variants and adds a regression guard.\n\nValidation: ==> release version gate (prevent downgrade/re-publish)
uv run python scripts/check_release_version.py
==> 版本门禁:本地 ksadk=0.8.0
✅ ksadk: 本地版本 0.8.0 > PyPI 已发版本 0.7.0
✅ agentengine-sdk-python: 本地版本 0.8.0 > PyPI 已发版本 0.7.0
✅ 版本门禁通过:本地版本 0.8.0 高于所有已发版本
==> secret and sensitive-file audit
✅ secret audit passed
==> public source audit
target: public-repo
checked: 1128
violations: 0
✅ public path audit passed
Sync KsADK Web static assets from @kingsoftcloud/ksadk-web@0.3.0
Using cached tarball kingsoftcloud-ksadk-web-0.3.0.tgz
tar -xzf ".cache/ksadk-web/$(cat ".cache/ksadk-web/.tarball-name")" -C ".cache/ksadk-web"
cp -R ".cache/ksadk-web/package/dist-ksadk/." "ksadk/server/static/"
Verified KsADK Web 0.3.0 static payload: 251 files, sha256=2ed4045a00a2ff9e92145cc0bd647e318dea1ff2f2a86aab3db183f9a1218011
Synced KsADK Web 0.3.0 static assets into ksadk/server/static
==> test
============================= test session starts ==============================
platform darwin -- Python 3.13.11, pytest-9.0.2, pluggy-1.6.0
rootdir: /private/tmp/ksadk-python-public-0.8.0-1785310789004
configfile: pyproject.toml
plugins: anyio-4.12.1, asyncio-1.3.0, langsmith-0.8.5
asyncio: mode=Mode.AUTO, debug=False, asyncio_default_fixture_loop_scope=None, asyncio_default_test_loop_scope=function
collected 45 items

tests/test_public_release_positioning.py ............... [ 33%]
tests/test_config_env_registry.py ..... [ 44%]
tests/test_managed_runtime_builder.py ........ [ 62%]
tests/test_managed_runtime_resolution.py ...... [ 75%]
tests/cli/test_cmd_create_codex.py ...... [ 88%]
tests/runners/test_codex_runner.py ..... [100%]

============================== 45 passed in 1.10s ==============================
==> docs-site (Fumadocs) build
Lockfile is up to date, resolution step is skipped
Already up to date

ksadk-docs-scaffold@0.0.0 postinstall /private/tmp/ksadk-python-public-0.8.0-1785310789004/docs-site
fumadocs-mdx

[MDX] generated files in 18.113166999999976ms
╭ Warning ─────────────────────────────────────────────────────────────────────╮
│ │
│ Ignored build scripts: esbuild@0.28.1, sharp@0.34.5. │
│ Run "pnpm approve-builds" to pick which dependencies should be allowed │
│ to run scripts. │
│ │
╰──────────────────────────────────────────────────────────────────────────────╯
Done in 1.5s using pnpm v10.33.2

ksadk-docs-scaffold@0.0.0 build:static /private/tmp/ksadk-python-public-0.8.0-1785310789004/docs-site
node scripts/build-static.mjs

▲ Next.js 16.2.6 (Turbopack)

[MDX] generated files in 359.8837500000001ms
Creating an optimized production build ...
✓ Compiled successfully in 21.9s
Running TypeScript ...
Finished TypeScript in 4.2s ...
Collecting page data using 10 workers ...
Generating static pages using 10 workers (0/193) ...
Generating static pages using 10 workers (48/193)
Generating static pages using 10 workers (96/193)
Generating static pages using 10 workers (144/193)
✓ Generating static pages using 10 workers (193/193) in 4.1s
Finalizing page optimization ...

Route (app)
┌ ○ /
├ ○ /_not-found
├ ● /[lang]
│ ├ /cn
│ └ /en
├ ● /[lang]/docs/[[...slug]]
│ ├ /cn/docs/cli
│ ├ /cn/docs/framework
│ ├ /cn/docs/references/environment-variables
│ └ [+89 more paths]
├ ○ /api/search
├ ○ /llms-full.txt
├ ● /llms.mdx/docs/[[...slug]]
│ ├ /llms.mdx/docs/cli/content.md
│ ├ /llms.mdx/docs/framework/content.md
│ ├ /llms.mdx/docs/references/environment-variables/content.md
│ └ [+43 more paths]
├ ○ /llms.txt
└ ● /og/docs/[...slug]
├ /og/docs/cli/image.png
├ /og/docs/framework/image.png
├ /og/docs/references/environment-variables/image.png
└ [+43 more paths]

○ (Static) prerendered as static content
● (SSG) prerendered as static HTML (uses generateStaticParams)

[build:static] wrote out/.nojekyll
🧹 清理 dist/build 临时产物...
==> build and twine check
Verified KsADK Web 0.3.0 static payload: 251 files, sha256=2ed4045a00a2ff9e92145cc0bd647e318dea1ff2f2a86aab3db183f9a1218011
................. [100%]
17 passed in 0.30s
Checking dist/ksadk-0.8.0-py3-none-any.whl: PASSED
Checking dist/ksadk-0.8.0.tar.gz: PASSED
==> audit wheel and sdist file lists
target: wheel
checked: 578
violations: 0
target: sdist
checked: 649
violations: 0
✅ public preflight passed (45 release-gate tests, docs build, wheel/sdist and secret audits).