Fix strict lookup in compat mode

[theodorejb]

Fixes #2149, fixes #1741

[Copilot]

Pull request overview

Fixes incorrect strict lookups when compat mode is enabled, preventing TypeError crashes and restoring expected strict error behavior.

Changes:

• Added strict+compat regression tests covering boolean block contexts, each item lookups, recursion, and null handling.
• Introduced a runtime helper (container.strictLookup) to safely traverse depths for strict property resolution in compat scenarios.
• Updated the JS compiler to emit container.strictLookup(...) when compat mode has already performed a depthed lookup.

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 2 comments.

File	Description
spec/strict.js	Adds test coverage for strict+compat mode behaviors and regressions.
lib/handlebars/runtime.js	Adds container.strictLookup to safely resolve strict properties across depths in compat mode.
lib/handlebars/compiler/javascript-compiler.js	Emits container.strictLookup(...) in the strict+compat codegen path to avoid in operator crashes on primitives.

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[kibertoad]

One suggestion: add a direct "{{v}} with strict+compat where v doesn't exist at any depth" test. Your "still throw when a property is missing at all depths" covers the same code path but via {{#each items}}, and a minimal top-level case would more clearly regress-guard the originally reported form.

[theodorejb]

@kibertoad I rebased now and added a test case for a simple {{v}} template where the variable is missing.

[kibertoad]

thank you!