docs: add public showcase pages and experimental value path

[huangruiteng]

Summary\n- add the public-safe showcase case pages and richer showcase catalog metrics\n- add an experimental Today Value Path below the first viewport in README, README.zh-CN, Frontstage, and showcase index\n- record the owner-review gate for public first-screen changes in AGENTS.md\n\n## Notes\n- the canonical Chinese hardware showcase page is preserved unchanged\n- P0 blocked -> safe fallback is documented as a repository kernel behavior inside an active goal, not as a standalone user command\n- unrelated benchmark/skillsbench local changes were left unstaged\n\n## Validation\n- python3 examples/showcase-html-pages.py --check\n- python3 examples/showcase-catalog-smoke.py\n- npm --prefix apps/dashboard run smoke:frontstage-route\n- npm --prefix apps/dashboard run build\n- git diff --check\n- loopx check --scan-path README.md --scan-path README.zh-CN.md --scan-path AGENTS.md --scan-path docs/showcases --scan-path examples/showcase-html-pages.py --scan-path examples/showcase-catalog-smoke.py --scan-path apps/dashboard/src/views/frontstage-page.tsx

[huangruiteng]

Self-review passed after resolving conflicts against current main.\n\nChecked:\n- Merged current main into the PR branch and resolved generated showcase conflicts by preserving the PR showcase version on top of current main. PR is now mergeable at 5180af0.\n- Verified the canonical Chinese hardware showcase HTML is not part of the PR diff; only the English generated page and MD heading/metadata path changed.\n- Verified the Experimental Today Value Path is below the existing showcase/Frontstage first-screen flow: README sections are below the showcase area, static showcase index places the experiment after the main case cards, and Frontstage renders it after ShowcaseMotionBoard.\n- Verified P0 blocked -> safe fallback is described as kernel behavior inside an active /loopx goal, not as a standalone command.\n- Public/private boundary scan is clean for the touched public paths.\n\nValidation run locally:\n- python3 examples/showcase-html-pages.py --check\n- python3 examples/showcase-catalog-smoke.py\n- npm --prefix apps/dashboard ci\n- npm --prefix apps/dashboard run smoke:frontstage-route\n- npm --prefix apps/dashboard run build\n- git diff --check / git diff --cached --check\n- loopx check --scan-path README.md --scan-path README.zh-CN.md --scan-path AGENTS.md --scan-path docs/showcases --scan-path examples/showcase-html-pages.py --scan-path examples/showcase-catalog-smoke.py --scan-path apps/dashboard/src/views/frontstage-page.tsx\n\nRemote GitHub build is green; deploy is skipped. I cannot GitHub-approve because this account owns the PR, and I am not self-merging from this side-agent lane because the final PR still touches 25 public showcase/frontstage files and ~800 lines, so it is outside the small validated side-agent self-merge bucket.

[huangruiteng]

Owner authorized self-merge in chat after first-screen review. Normal squash merge is blocked by branch policy (reviewDecision=REVIEW_REQUIRED), so I am using maintainer/admin self-merge for this owner-approved docs/showcase/frontstage PR.

Validation rerun before merge:

• python3 examples/showcase-html-pages.py --check
• python3 examples/showcase-catalog-smoke.py
• npm --prefix apps/dashboard run smoke:frontstage-route
• npm --prefix apps/dashboard run build
• git diff --check origin/main...HEAD
• python3 -m loopx.cli --format json check --scan-path README.md --scan-path README.zh-CN.md --scan-path AGENTS.md --scan-path docs/showcases --scan-path examples/showcase-html-pages.py --scan-path examples/showcase-catalog-smoke.py --scan-path apps/dashboard/src/views/frontstage-page.tsx

Boundary: public/private scan is clean for touched public paths. Existing LoopX history duplicate-index warning is unrelated. Merge decision: self-merged with owner authorization.