WASM-inline: support CS_WORKSPACE_CRN / derive region from workspace CRN

[coderdan]

Follow-up from #496 / #522. The existing CRN tracking issue covers the Rust crate; this is the equivalent gap in @cipherstash/stack.

Problem

The WASM-inline entry (@cipherstash/stack/wasm-inline) currently:

• Ignores CS_WORKSPACE_CRN — the WASM client derives workspace identity from the access-key token, not from the CRN. The Node entry consumes the CRN, so this is a parity gap. examples/supabase-worker/.env.example and the wasm-e2e-tests CI job both deliberately omit the var with a comment pointing here.
• Requires region explicitly — WasmClientConfig.region is a required field, marked @deprecated in packages/stack/src/wasm-inline.ts, because the underlying @cipherstash/auth/wasm-inline AccessKeyStrategy.create() still takes a region argument.

Desired end state

Once @cipherstash/auth switches AccessKeyStrategy.create() to take a workspaceCrn and derive the region from it:

• Replace the required region field with workspaceCrn on WasmClientConfig (single source of truth).
• Assert the bearer token's workspace against the CRN.
• Re-add CS_WORKSPACE_CRN to the Supabase example .env.example + the wasm-e2e-tests job env, and remove the "deliberately omitted" comments.
• Update the region deprecation note / docs accordingly.

Blocked on

A @cipherstash/auth/wasm-inline release whose AccessKeyStrategy.create() accepts a workspaceCrn.

See the region deprecation comment in packages/stack/src/wasm-inline.ts for context.