[WhitWaldo]

Description

This PR hardens Actors.Next ahead of the v1.19 release, addressing concurrency, correctness, and reliability issues across the framework:

• Fixes reentrancy propagation, mailbox deadlocks, stream recovery, scheduling races, and deactivation during active turns
• Improves state persistence, migration, legacy-envelope compatibility, identity serialization, and recovery from failed activation
• Coordinates cache eviction with in-flight commits and tracks mutations within reference-containing structs
• Preserves mutations made during an in-flight state commit—including reverting a value to its previous durable value—so subsequent saves cannot incorrectly treat newer state as clean
• Stabilizes state-envelope metadata across custom JSON naming policies and explicitly rejects malformed envelopes
• Corrects state-machine initialization, timer dispatch, failed-event handling, and hierarchical handler precedence, including deferred-event replay
• Gives hierarchical state timeouts independent ownership, allowing parent and child deadlines to coexist and preserving parent deadlines across sibling-state transitions
• Adds timeout-generation validation so callbacks queued before a timeout is restarted, extended, or canceled cannot affect the replacement registration
• Ties in-memory actor timers to activation lifetime, ensuring they are stopped after normal deactivation, failed activation, factory failure, or disposal failure without removing durable reminders
• Enforces in-memory reminder TTLs and safely cleans up expired registrations
• Fixes generated-code edge cases and cross-assembly registration, deduplicates inherited contract methods, and reports incompatible wire-name collisions
• Reduces generator memory usage and resolves build-time memory exhaustion
• Expands unit, allocation, generated-proxy, and Dapr runtime integration coverage, including test-runtime isolation, migration persistence, actor reactivation, concurrent state mutation, queued timeout replacement, hierarchical deadlines, and timer cleanup across activation boundaries
• Strengthens the Auction example’s deterministic soft-close race test so an already-queued original timeout is rejected after a last-second bid reschedules the deadline
• Clarifies that the Cart example uses an activation-local timer rather than a durable reminder and corrects its Dapr app-channel launch port in the documentation

Issue reference

We strive to have all PR being opened based on an issue, where the problem or feature have been discussed prior to implementation.

Please reference the issue this PR will close: #[issue number]

Checklist

Please make sure you've completed the relevant tasks for this PR, out of the following list:

• Code compiles correctly
• Created/updated tests
• Extended the documentation

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 65.85%. Comparing base (fa7e0f7) to head (56af183).

Additional details and impacted files

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##           master    #1938   +/-   ##
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  Coverage   65.85%   65.85%           
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  Files         372      372           
  Lines       10774    10774           
  Branches     1264     1264           
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  Hits         7095     7095           
  Misses       3348     3348           
  Partials      331      331           

Flag	Coverage Δ
net10.0	65.83% <ø> (ø)

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