Add feature-gated js_repl polling flow

[fjord-oai]

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git stack

• ✅ 01 Add feature-gated freeform js_repl core runtime #10674
• ✅ 02 Add js_repl host helpers and exec end events #10672
• ✅ 03 Add js_repl_tools_only model and routing restrictions #10671
• ✅ 04 Add js_repl kernel crash diagnostics #11666
• ✅ 05 Fix js_repl view_image test runtime panic #11796
• ✅ 06 Fix js_repl in-flight tool-call waiter race #11800
• ✅ 07 Stop filtering model tools in js_repl_tools_only mode #12069
• ✅ 08 Add optional js_repl isolation and vendored Node runtime #10670
• ✅ 09 js_repl: canonicalize paths for node_modules boundary checks #12177
• ⏳ 10 js_repl: block wrapped payload prefixes in grammar #12300
• ⏳ 11 js_repl: remove codex.state helper references #12275
• ⏳ 12 ci(bazel): install Node from node-version.txt in remote image #12205
• ⏳ 13 tests(js_repl): remove node-related skip paths from js_repl tests #12185
• 👉 14 Add feature-gated js_repl polling flow #10673