feat: session-configurable reasoning effort + media provider aliases

[rita-aga]

Two clean features on top of current main (the earlier blind Genesis→GitHub mirror was reverted — see the divergence note below).

1. Session-configurable reasoning effort (provider_caller): the codex/OpenAI Responses call reads reasoning_effort from the session's provider_options_json ({"reasoning_effort":"minimal|low|medium|high"}); absent/invalid keeps the prior hardcoded medium. katagami synthesis will set high — the hardcoded medium is the prime suspect for identical/safe design output across independent runs of a brief.

2. Media provider aliases + hint (paw-media): openai (and obvious spellings) → openai_codex, the sole v1 provider. Both observed hero-image failures (Mullion, Madori) burned a first attempt on the openai guess. The Generate action hint names valid values so the Code-Mode typed reference surfaces the contract.

Both wasm rebuilt; module + paw_fs_hot_path/session_turn_architecture/datadog_observability_contract suites green.

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⚠️ Divergence discovered (needs a decision, not part of this PR): production paw-agent installs from a long-lived Genesis branch codex/paw-agent-main-session-storage-20260621 that never merged back to GitHub main. main and that branch have diverged bidirectionally — main is ahead on some modules (e.g. artifact_batch_apply bounded_reads), the deployment branch is ahead on others (workspace_fs resolver fix, monty_repl files channel, typed-session Fail steering — my earlier work, currently only on Genesis). A blind mirror regresses main; a blind reverse regresses production. Reconciling the two lineages (or picking one canonical) is an architectural call (ARN-69 territory). Filed for follow-up.

🤖 Generated with Claude Code

Greptile Summary

This PR makes OpenAI reasoning effort session-configurable and expands accepted media-provider aliases.

• Reads an allowlisted reasoning_effort from provider_options_json, retaining medium as the default.
• Advertises media-provider values and normalizes additional OpenAI Codex aliases.

Confidence Score: 5/5

The PR appears safe to merge because no blocking failure remains within the eligible follow-up scope.

No blocking failure remains.

Important Files Changed

Filename	Overview
os-apps/paw-agent/wasm/provider_caller/src/lib.rs	Adds allowlisted reasoning-effort selection to OpenAI Responses requests and unit coverage for defaults and supported values.
os-apps/paw-media/specs/media_generation.ioa.toml	Expands the Generate action hint with supported provider and operation guidance.
os-apps/paw-media/wasm/openai_codex_image_generate/src/lib.rs	Adds common OpenAI Codex provider spellings to image-generation request normalization.

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