fix(sidebar): restore visible reorder animation

[Tryanks]

Summary

• keep each virtual-list item root stationary and apply the spring offset to an inner row
• preserve the existing stable per-session spring identity and reorder geometry
• replace the synthetic flex-box probe with a regression test that exercises the real virtual list and rendered row bounds

Root cause

GPUI positions every virtual-list item root explicitly during prepaint. The previous implementation applied the relative spring offset to that root, so prepaint overwrote the offset and the rows visibly snapped to their new indices even though the spring itself was running.

Test plan

• cargo test -p tcode-ui
• cargo test -p tcode-ui sidebar::tests
• cargo clippy -p tcode-ui --tests -- -D warnings
• cargo fmt --all -- --check

[Tryanks]

Summary

• keep each virtual-list item root stationary and apply the spring offset to an inner row
• preserve the existing stable per-session spring identity and reorder geometry
• replace the synthetic flex-box probe with a regression test that exercises the real virtual list and rendered row bounds

Root cause

GPUI positions every virtual-list item root explicitly during prepaint. The previous implementation applied the relative spring offset to that root, so prepaint overwrote the offset and the rows visibly snapped to their new indices even though the spring itself was running.

Test plan

• cargo test -p tcode-ui
• cargo test -p tcode-ui sidebar::tests
• cargo clippy -p tcode-ui --tests -- -D warnings
• cargo fmt --all -- --check

[Tryanks]

Summary

• keep each virtual-list item root stationary and apply the spring offset to an inner row
• preserve the existing stable per-session spring identity and reorder geometry
• replace the synthetic flex-box probe with a regression test that exercises the real virtual list and rendered row bounds

Root cause

GPUI positions every virtual-list item root explicitly during prepaint. The previous implementation applied the relative spring offset to that root, so prepaint overwrote the offset and the rows visibly snapped to their new indices even though the spring itself was running.

Test plan

• cargo test -p tcode-ui
• cargo test -p tcode-ui sidebar::tests
• cargo clippy -p tcode-ui --tests -- -D warnings
• cargo fmt --all -- --check

[Tryanks]

Summary

• keep each virtual-list item root stationary and apply the spring offset to an inner row
• preserve the existing stable per-session spring identity and reorder geometry
• replace the synthetic flex-box probe with a regression test that exercises the real virtual list and rendered row bounds

Root cause

GPUI positions every virtual-list item root explicitly during prepaint. The previous implementation applied the relative spring offset to that root, so prepaint overwrote the offset and the rows visibly snapped to their new indices even though the spring itself was running.

Test plan

• cargo test -p tcode-ui
• cargo test -p tcode-ui sidebar::tests
• cargo clippy -p tcode-ui --tests -- -D warnings
• cargo fmt --all -- --check

[Tryanks]

Summary

• keep each virtual-list item root stationary and apply the spring offset to an inner row
• preserve the existing stable per-session spring identity and reorder geometry
• replace the synthetic flex-box probe with a regression test that exercises the real virtual list and rendered row bounds

Root cause

GPUI positions every virtual-list item root explicitly during prepaint. The previous implementation applied the relative spring offset to that root, so prepaint overwrote the offset and the rows visibly snapped to their new indices even though the spring itself was running.

Test plan

• cargo test -p tcode-ui
• cargo test -p tcode-ui sidebar::tests
• cargo clippy -p tcode-ui --tests -- -D warnings
• cargo fmt --all -- --check

[Tryanks]

Summary

• keep each virtual-list item root stationary and apply the spring offset to an inner row
• preserve the existing stable per-session spring identity and reorder geometry
• replace the synthetic flex-box probe with a regression test that exercises the real virtual list and rendered row bounds

Root cause

GPUI positions every virtual-list item root explicitly during prepaint. The previous implementation applied the relative spring offset to that root, so prepaint overwrote the offset and the rows visibly snapped to their new indices even though the spring itself was running.

Test plan

• cargo test -p tcode-ui
• cargo test -p tcode-ui sidebar::tests
• cargo clippy -p tcode-ui --tests -- -D warnings
• cargo fmt --all -- --check

[Tryanks]

Summary

• keep each virtual-list item root stationary and apply the spring offset to an inner row
• preserve the existing stable per-session spring identity and reorder geometry
• replace the synthetic flex-box probe with a regression test that exercises the real virtual list and rendered row bounds

Root cause

GPUI positions every virtual-list item root explicitly during prepaint. The previous implementation applied the relative spring offset to that root, so prepaint overwrote the offset and the rows visibly snapped to their new indices even though the spring itself was running.

Test plan

• cargo test -p tcode-ui
• cargo test -p tcode-ui sidebar::tests
• cargo clippy -p tcode-ui --tests -- -D warnings
• cargo fmt --all -- --check

[Tryanks]

Summary

• keep each virtual-list item root stationary and apply the spring offset to an inner row
• preserve the existing stable per-session spring identity and reorder geometry
• replace the synthetic flex-box probe with a regression test that exercises the real virtual list and rendered row bounds

Root cause

GPUI positions every virtual-list item root explicitly during prepaint. The previous implementation applied the relative spring offset to that root, so prepaint overwrote the offset and the rows visibly snapped to their new indices even though the spring itself was running.

Test plan

• cargo test -p tcode-ui
• cargo test -p tcode-ui sidebar::tests
• cargo clippy -p tcode-ui --tests -- -D warnings
• cargo fmt --all -- --check