Align wasm-inline entry to config.authStrategy (currently uses config.strategy)

[coderdan]

Follow-up from #562, raised by Copilot review.

#562 renamed the Node Encryption() client's auth field from config.strategy to config.authStrategy (keeping strategy as a deprecated alias). The @cipherstash/stack/wasm-inline entry (Deno / Edge / Workers / Bun) still exposes the strategy under config.strategy — via WasmClientConfig and resolveStrategy in packages/stack/src/wasm-inline.ts. This leaves the package with two different field names for the same concept depending on entry point.

Why it was deferred from #562

The wasm path is not a straight rename: WasmClientConfig is a discriminated union where strategy is mutually exclusive with accessKey (strategy?: never on the access-key arm, strategy: WasmAuthStrategy on the other), and resolveStrategy enforces that at runtime for plain-JS/Deno callers. Adding an authStrategy alias means widening the union to a three-way shape and updating the mutual-exclusivity guards + wasm tests — larger and higher-risk than the focused Node rename, so it was kept out to keep #562 reviewable.

Scope

• Add authStrategy to WasmClientConfig as the documented field; keep strategy as a deprecated alias.
• Update resolveStrategy to read authStrategy ?? strategy, preserving the accessKey mutual-exclusivity guard against both fields.
• Update the wasm-inline top-level docs/examples and the offline resolveStrategy tests.
• Decide whether the wasm path needs a runtime deprecation warning too (Node emits one).

Related

• feat(stack): rename config.strategy to authStrategy; document auth + keysets #562 — the Node-side rename.

[coderdan]

Plan changed — rather than a follow-up, this is now implemented in #562 so the Node and WASM interfaces stay in sync (commit db9a756). WasmClientConfig.authStrategy is the documented field, strategy is a deprecated alias that warns at runtime, and resolveStrategy resolves authStrategy ?? strategy with the mutual-exclusivity guard covering both fields. This issue will auto-close when #562 merges.