Avoid root dirty delta for shared state events

[harsh21234i]

Summary

• Preserve and restore root dirty state around the temporary router dirtying used by linked/shared state patching.
• Prevent regular linked-state events from sending an unchanged root/router delta.
• Add regression coverage for the issue described in Events against SharedState should not mark root state dirty all the time #6392.

Tests

• uv run --frozen pytest tests/units/test_state.py::test_linked_state_event_does_not_dirty_root_state -q
• uv run --frozen pytest tests/units/test_state.py::test_linked_state_event_does_not_dirty_root_state tests/units/test_state.py::test_router_var_dep tests/units/test_state.py::test_computed_var_depends_on_parent_non_cached tests/units/test_state.py::test_async_computed_var_get_state -q
• uv run --frozen pytest tests/units/test_state.py -q
• uv run --frozen pre-commit run --files reflex/istate/shared.py tests/units/test_state.py news/6392.bugfix.md

Closes #6392

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[codspeed-hq]

Merging this PR will not alter performance

✅ 26 untouched benchmarks
⏩ 8 skipped benchmarks¹

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_{Comparing harsh21234i:fix/shared-state-root-dirty-6392 (c19e5a2) with main (a348aea)}

Footnotes

1. 8 benchmarks were skipped, so the baseline results were used instead. If they were deleted from the codebase, click here and archive them to remove them from the performance reports. ↩

[greptile-apps]

Greptile Summary

This PR prevents temporary router dirtiness used during linked/shared-state patching from leaking into regular event deltas and now restores that dirtiness when resolution raises.

• Snapshots and restores root dirty variables and substates for non-full linked-state patches.
• Adds regression coverage for normal linked-state events and exceptional delta resolution.
• Corrects the changelog category for an earlier entry.

Confidence Score: 5/5

The PR appears safe to merge.

No blocking failure remains; the previously reported exceptional-resolution leak is addressed by nested finally blocks that restore both dirty state and patched tree links, with regression coverage for the error path.

Important Files Changed

Filename	Overview
reflex/istate/shared.py	Preserves root dirty-state snapshots around temporary router-dependent delta resolution and restores them in a finally block for regular linked-state events.
tests/units/test_state.py	Adds focused regression tests covering clean regular-event deltas and dirty-state/tree-link restoration after resolution errors.
news/6841.bugfix.md	Documents the linked/shared-state temporary router-dirtiness fix.
news/6836.misc.md	Reclassifies an existing changelog entry from chore to misc.

_{Reviews (3): Last reviewed commit: "Use valid news fragment type for Pillow ..." | Re-trigger Greptile}

[cubic-dev-ai]

All reported issues were addressed across 3 files

<sub>Reply with feedback, questions, or to request a fix.

Fix all with cubic | Re-trigger cubic</sub>