Validation: Add immediate data pipeline validation tests

[shaoboyan091]

Adds pipeline_immediate.spec.ts to validate immediate data usage in RenderPassEncoder, ComputePassEncoder, and RenderBundleEncoder.

Tests cover:

• Required immediate data slots are set.
• Unused variables do not require slots.
• Pipeline creation fails if shader immediate size exceeds layout limit.
• RenderBundle execution invalidates pipeline and immediate data state.

Issue: #

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Requirements for PR author:

• All missing test coverage is tracked with "TODO" or .unimplemented().
• New helpers are /** documented */ and new helper files are found in helper_index.txt.
• Test behaves as expected in a WebGPU implementation. (If not passing, explain above.)
• Test have be tested with compatibility mode validation enabled and behave as expected. (If not passing, explain above.)

Requirements for reviewer sign-off:

• Tests are properly located in the test tree.
• Test descriptions allow a reader to "read only the test plans and evaluate coverage completeness", and accurately reflect the test code.
• Tests provide complete coverage (including validation control cases). Missing coverage MUST be covered by TODOs.
• Helpers and types promote readability and maintainability.

When landing this PR, be sure to make any necessary issue status updates.

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Pull request overview

Copilot reviewed 2 out of 2 changed files in this pull request and generated 5 comments.

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[github-actions]

Results for build job (at bed2542):

+webgpu:api,validation,createPipelineLayout:immediate_data_size:* - 8 cases, 8 subcases (~1/case)
+webgpu:api,validation,encoding,programmable,pipeline_immediate:required_slots_set:* - 69 cases, 69 subcases (~1/case)
+webgpu:api,validation,encoding,programmable,pipeline_immediate:unused_variable:* - 18 cases, 18 subcases (~1/case)
+webgpu:api,validation,encoding,programmable,pipeline_immediate:overprovisioned_immediate_data:* - 3 cases, 3 subcases (~1/case)
+webgpu:api,validation,encoding,programmable,pipeline_immediate:pipeline_creation_immediate_size_mismatch:* - 3 cases, 3 subcases (~1/case)
+webgpu:api,validation,encoding,programmable,pipeline_immediate:render_bundle_execution_state_invalidation:* - 4 cases, 4 subcases (~1/case)
-TOTAL: 284493 cases, 2341915 subcases
+TOTAL: 284598 cases, 2342020 subcases

[Copilot]

Pull request overview

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

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Pull request overview

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

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[Copilot]

Pull request overview

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

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[Copilot]

The 'function_unused' scenario doesn't fit the purpose of the 'required_slots_set' test, which is meant to validate that required immediate data slots are set. This scenario tests when data is NOT statically used and therefore slots are NOT required. Consider moving this scenario to the 'unused_variable' test or removing it if redundant with that test's coverage.

Suggested change

'function_unused',

[Copilot]

The comment "Vector (size 16), functions (size 16), dynamic_indexing (size 16)" is incomplete as this else branch also handles the 'function_unused' scenario. Update the comment to explicitly list all scenarios handled in this branch: "Vector (size 16), functions (size 16), function_unused (size 16), dynamic_indexing (size 16)"

Suggested change

	// Vector (size 16), functions (size 16), dynamic_indexing (size 16)
	// Vector (size 16), functions (size 16), function_unused (size 16), dynamic_indexing (size 16)

[kainino0x]

Sorry, bit swamped. Should be able to review tomorrow.