fix(core): prevent TLA hang when has_tick_scheduled is set during async module evaluation

[bartlomieju]

Summary

• Fix module evaluation promise getting permanently stuck in Pending when has_tick_scheduled is true during async module evaluation with TLA
• Replace unreachable!() panic with graceful recovery when V8 reports no stalled TLA but evaluation is still pending

Fixes #32821

Root cause

PR #32466 added a has_tick_scheduled() guard to the microtask checkpoint in mod_evaluate (map.rs:1572). For async module graphs with TLA, this checkpoint is critical for draining V8's TLA resume microtasks. When CJS module initialization calls process.nextTick() (setting has_tick_scheduled = true), the checkpoint is skipped, which can leave the evaluation promise permanently Pending in large module graphs.

Changes

libs/core/modules/map.rs -- Primary fix:

• Always run the microtask checkpoint for async module graphs (is_graph_async), regardless of has_tick_scheduled
• The nextTick ordering concern only applies to user-visible promise callbacks, not to V8's internal TLA resolution

libs/core/runtime/jsruntime.rs -- Safety net:

• Replace unreachable!("Expected at least one stalled top-level await") with graceful handling
• Try one last microtask checkpoint before reporting a stalled TLA
• If V8 reports no stalled TLAs but evaluation is still pending, retry the event loop iteration instead of panicking

libs/core/modules/tests.rs -- Regression test:

• test_tla_with_tick_scheduled_no_hang: verifies async module evaluation with TLA completes when has_tick_scheduled is set during evaluation

Test plan

• New test: test_tla_with_tick_scheduled_no_hang -- async module graph with TLA + tick scheduled
• Existing test: test_lazy_loaded_esm_with_tla_no_panic -- still passes
• Existing test: test_stalled_tla -- stalled TLA error reporting still works
• Manual verification with the reporter's large module graph (500+ ESM modules, ~100 CJS packages)

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