Expose browser pool launch configuration

[IlyaasK]

Summary

• expose computed proxy_id, headless, kiosk_mode, and stealth on kernel_browser_pool
• preserve known false values through Terraform Framework state serialization
• return typed null only for omitted optional SDK fields
• reject explicit JSON null and malformed present values
• update generated Registry docs

Why this is v1 work

This is an additive durable read-only surface. It does not change v0 resources or introduce runtime/session operations. URL/rate settings, viewport, and Chrome policy remain separate PRs.

State semantics

SDK omission means the optional field is absent and maps to Terraform null. Explicit null is invalid because these SDK fields are non-nullable. Present booleans retain both true and false as known values.

Tests run

• go test -count=20 ./internal/datasources/browserpool
• go test -race ./internal/datasources/browserpool ./internal/provider
• go test -short -timeout=2m ./...
• go vet ./...
• gofmt, module verify/tidy diff, Terraform example fmt, docs drift, and diff checks

Tests cover omitted values, valid proxy/booleans, known false through Read -> State.Set -> State.Get, explicit null for all four fields, wrong types, and empty proxy IDs.

Acceptance status

Not run. Live response and project-scoping proof remains deferred to the opt-in acceptance slice.

Additional quality verification

• Gremlins: 27/27 mutants killed; targeted semantic mutations: 8/8 killed
• browser-pool data-source coverage: 92.0%; maximum CRAP score: 15.0
• Godog stack suite: 7 scenarios / 21 steps passed, including the @pr76 launch-configuration scenario

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Note

Low Risk
Additive computed-only data source fields with strict read-time validation; no resource or write-path changes.

Overview
Adds read-only launch settings to the kernel_browser_pool data source: proxy_id, headless, kiosk_mode, and stealth, mapped from browser_pool_config in the Kernel API response. Registry docs list the new computed attributes.

Flattening treats omitted optional SDK fields as Terraform null, keeps known false booleans (not collapsed to null), and surfaces diagnostics for explicit JSON null, wrong types, and invalid proxy_id values. Shared helpers flattenOptionalString, flattenOptionalBool, and validResponseBool implement that behavior alongside existing response validation.

Tests cover schema presence, read/state round-trip, happy-path flattening, and invalid launch-configuration payloads.

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