[Mastersam07]

Closes #90

When a main router guard rewrites a navigation and the main stack changes as a result, KaiselRouter now closes every open modal flow, topmost first, and each run resolves with null. Before, the flow stayed on top and hid the screen the guard sent the user to, so signing out mid flow left the flow over Login.

When flows close

• A guard's output differs from the proposal and the main stack actually changed. This covers reevaluate / reevaluateOn (sign out, session expiry, app lock) and redirected pushes.

When they stay open

• No guard rewrote the navigation (ordinary pushes while a flow is open).
• A guard refused the change, so the stack stayed where it was.
• A guard on a flow's own router redirected inside the flow.

Behaviour change. Marked as such in both changelogs. One consequence worth knowing: a lock guard that appends a passcode screen now closes an open flow too. That is the safer outcome, since before the flow covered the lock screen.

Tests

• kaisel_core/test/kaisel_flow_redirect_test.dart: redirect via reevaluate, redirected push, nested flows, plus the three keep open cases. The three closing tests fail without the fix.
• kaisel/test/kaisel_flow_redirect_test.dart: widget test for the issue's case, sign out mid flow with reevaluateOn; Login shows and the flow UI is gone. Without the fix it hangs on the flow result.

Docs. The guards guide and modal flows guide now describe the new behaviour and drop the dismissFlow listener workaround.

[github-actions]

📖 Docs preview: https://kaisel.dev/pr-101/ (updates on every push; removed when this PR closes)

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 99.66%. Comparing base (84a3a08) to head (092c3b4).
⚠️ Report is 5 commits behind head on dev.

Additional details and impacted files

@@           Coverage Diff           @@
##              dev     #101   +/-   ##
=======================================
  Coverage   99.66%   99.66%           
=======================================
  Files          43       43           
  Lines        2409     2418    +9     
=======================================
+ Hits         2401     2410    +9     
  Misses          8        8           

Flag	Coverage Δ
kaisel	99.66% <100.00%> (+<0.01%)	⬆️
kaisel_core	99.66% <100.00%> (+<0.01%)	⬆️
kaisel_devtools	99.66% <100.00%> (+<0.01%)	⬆️
kaisel_lint	99.66% <100.00%> (+<0.01%)	⬆️

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