feat(render-html): Serialize collapse state in URL and support popstate navigation

[mhiro2]

Summary

• Serialize table collapse state into the URL hash (c parameter) so it can be shared and
  bookmarked
• Expose a runtime API (runtime.collapse.getCollapsed / runtime.collapse.setCollapsed) for
  programmatic collapse control
• Support browser back/forward navigation via popstate with proper pushState/replaceState
  distinction

Changes

• c748081 : feat(render-html): serialize collapse state in URL and support popstate navigation
  • Add ViewerCollapseApi interface with getCollapsed/setCollapsed methods to
    viewer_api.ts, extending ViewerRuntime and ViewerModule types
  • Implement applyCollapseState in collapse.ts for programmatic collapse/expand, register
    the collapse module in the viewer runtime, and emit relune:collapse-changed events on toggle
  • Serialize collapsed table IDs as the c hash parameter in url_state.ts, restore them on
    page load, and validate IDs against known table IDs; introduce scheduleDiscreteWrite using
    history.pushState for user actions while keeping history.replaceState for continuous viewport
    changes; add popstate listener with restoringFromPopstate guard to avoid duplicate history
    entries

[github-actions]

Code Metrics Report

	main (a9d8da7)	#48 (6ad409a)	+/-
Coverage	94.1%	94.1%	0.0%
Test Execution Time	1m34s	1m38s	+4s

Details

  |                     | main (a9d8da7) | #48 (6ad409a) | +/-  |
  |---------------------|----------------|---------------|------|
  | Coverage            |          94.1% |         94.1% | 0.0% |
  |   Files             |             77 |            77 |    0 |
  |   Lines             |          29895 |         29895 |    0 |
  |   Covered           |          28148 |         28148 |    0 |
- | Test Execution Time |          1m34s |         1m38s |  +4s |

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Reported by octocov