fix(rivetkit-native): expose full hibernation metadata to JS

[NathanFlurry]

Description

Please include a summary of the changes and the related issue. Please also include relevant motivation and context.

Type of change

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• This change requires a documentation update

How Has This Been Tested?

Please describe the tests that you ran to verify your changes.

Checklist:

• My code follows the style guidelines of this project
• I have performed a self-review of my code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• My changes generate no new warnings
• I have added tests that prove my fix is effective or that my feature works
• New and existing unit tests pass locally with my changes

[NathanFlurry]

Warning

This pull request is not mergeable via GitHub because a downstack PR is open. Once all requirements are satisfied, merge this PR as a stack on Graphite.
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• fix(guard): serialize gateway actor keys correctly #4655
• fix(api): subscribe before namespace workflow dispatch #4654
• fix(rivetkit): restore hibernatable sockets and hydrate serverless starts #4658
• fix(rivetkit-native): expose full hibernation metadata to JS #4657 👈 (View in Graphite)
• fix(pegboard): persist and replay hibernating requests #4656
• fix(rivetkit): keep internal error exposure behavior consistent #4661
• test(rivetkit): stabilize actor db driver tests #4664
• fix(test): stabilize lifecycle, sleep, queue, and run edge cases #4660 : 1 other dependent PR (#4665 )
• test(rivetkit): re-enable gateway URL and direct-registry coverage #4659
• chore(engine): publish engine bases in ci #4649 : 2 other dependent PRs (#4650 , #4652 )
• chore: lockfile lefthook #4647
• fix(rivetkit): surface native sqlite kv errors to callers #4645
• fix(rivetkit): prevent sleep races during disconnect and db work #4644
• fix(rivetkit): isolate engine envoys and propagate startup failures #4643
• test(rivetkit): remove wasm sqlite-only fixtures and coverage #4642
• chore(sqlite-vfs): remove wasm sqlite packages and workspace wiring #4641
• chore(rivetkit): remove wasm sqlite runtime #4614
• fix(sqlite-native): restore native startup kv preload #4639
• fix(sqlite-native): delete metadata before chunk range #4638
• fix(sqlite-native): keep truncate cache coherent #4637
• fix(sqlite-vfs): use delete range for truncate cleanup #4636
• fix(sqlite-native): restore kv error hook #4635
• perf(sqlite-native): avoid cloning cached read chunks #4634
• perf(sqlite-native): gate kv operation labels #4633
• perf(sqlite-native): reuse read cache for partial writes #4632
• perf(sqlite-native): remove delete file existence probe #4631
• fix(sqlite-native): gate native read cache behind env var #4630
• fix(pegboard): isolate runner config dc lookup failures #4625 : 1 other dependent PR (#4626 )
• docs(pegboard): note runner config upsert split write risk #4624
• fix(pegboard): unpack global runner config keys correctly #4623
• fix(pegboard-gateway): enforce tunnel message state #4622
• fix(pegboard-runner): clear terminal tunnel routes #4621
• fix(pegboard): skip protocol version keys in runner pool backfill #4620
• fix(pegboard): create missing normal runner configs #4619
• fix(epoxy): reuse cached optimistic value #4618
• main

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[claude]

PR Review

This PR fixes two genuine correctness bugs in the native envoy hibernation path.

1. can_hibernate was always returning false (stub), making WebSocket hibernation non-functional.
2. restore_hibernating_requests was restoring sessions with zeroed-out message indices, empty path, and empty headers.

Both are real bugs and the general approach is correct.

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Medium: ThreadsafeFunctionCallMode::Blocking should be NonBlocking in can_hibernate. Using Blocking mode can deadlock if the JS thread is already processing another TSFN call. Every other event_cb.call() in the file uses NonBlocking, and NonBlocking is sufficient since the response arrives via rx.blocking_recv().

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Low: Response map entry is leaked on error in can_hibernate. If rx.blocking_recv() returns Err, the entry for response_id is never removed from response_map. The async paths clean up correctly but the synchronous path does not.

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Low: The dual canHibernate call pattern is undocumented. wrapper.js calls canHibernate in two distinct places. A comment explaining when each is called would help maintainers.

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Nit: r.headers.unwrap_or_else(HashMap::new) is more idiomatic as r.headers.unwrap_or_default().

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Positive: Switching ResponseMap to std::sync::Mutex is correct given that can_hibernate is a synchronous fn using block_in_place. Keeping WsSenderMap as tokio::sync::Mutex is also correct.

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No tests added. The can_hibernate round-trip and hibernation restore with real metadata are non-trivial. An integration test covering the hibernation/wake-up cycle through the native bridge would help prevent regressions.