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.

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Note

Low Risk
Additive computed-only data source attributes with validation; no resources or write paths changed.

Overview
Adds read-only proxy_id, headless, kiosk_mode, and stealth to the kernel_browser_pool data source so Terraform can surface durable launch settings from browser_pool_config.

Flattening maps SDK omitted optional fields to Terraform null, keeps known false (and other present values) in state, and errors on explicit JSON null, wrong types, or invalid proxy_id (including empty string). Registry docs for the data source are updated accordingly.

Tests cover schema attributes, full read/state round-trip, happy-path flattening, and invalid API payloads for all four fields.

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