perf: batch fixed opponent life-loss triggers

[matthewevans]

Summary by CodeRabbit

• New Features

  • Improved resolution of repeated opponent life-loss effects by processing eligible consecutive triggers together.
  • Preserves resolution-time condition checks and safely stops batching when conditions or effect details differ.

• Bug Fixes

  • Prevents batch processing when life-loss observers or other effects could change the outcome.
  • Ensures triggers with differing prerequisites, targets, timing, or optionality continue to resolve individually.

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ℹ️ Recent review info

⚙️ Run configuration

Configuration used: Organization UI

Review profile: CHILL

Plan: Pro Plus

Run ID: b3e07d1e-7b85-4e45-8bb6-2d36768c84cf

📥 Commits

Reviewing files that changed from the base of the PR and between e06df32 and ffbfbe8.

📒 Files selected for processing (1)

• crates/engine/src/game/stack.rs

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📝 Walkthrough

Walkthrough

Adds Tier-3 batching for eligible fixed opponent life-loss triggered abilities, preserving intervening-if checks and resolved-context invariants through the proven-inert batch framework. Tests cover batching, rechecks, run boundaries, and observer-triggered fallback.

Changes

Opponent life-loss batching

Layer / File(s)	Summary
Fixed opponent life-loss batch implementation crates/engine/src/game/stack.rs	Adds strict eligibility checks, contiguous-run detection, batch keys, and proven-inert batch resolution for fixed opponent life-loss abilities.
Tier-3 resolution dispatch crates/engine/src/game/stack.rs	Routes eligible runs of at least two entries through the new batch resolver.
Batch construction and runtime validation crates/engine/src/game/stack.rs	Adds trigger helpers and tests for provenance, intervening-if reevaluation, differing conditions, and life-lost observer fallback.

Estimated code review effort: 4 (Complex) | ~45 minutes

Sequence Diagram(s)

sequenceDiagram
  participant StackResolver
  participant RunDetector
  participant BatchResolver
  participant ProvenInertFramework
  StackResolver->>RunDetector: inspect top contiguous opponent life-loss run
  RunDetector-->>StackResolver: return eligible run length
  StackResolver->>BatchResolver: resolve run when length is at least two
  BatchResolver->>ProvenInertFramework: prove and commit entries
  ProvenInertFramework-->>BatchResolver: apply entries passing intervening-if checks

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Suggested reviewers: lgray, andriypolanski, nornagon

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title clearly matches the main change: batching fixed opponent life-loss triggers for performance.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.

✨ Finishing Touches

📝 Generate docstrings

• Create stacked PR
• Commit on current branch

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch ship/batch-opponent-life-loss

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[matthewevans]

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