Improve first-run config and add 2048 demo recorder

[willamhou]

Summary

• add CLI config provider/model show/list/set commands and surface model/base URL in quickstart
• add a model-backed 2048 demo recorder with transcript, validation, optional preview server, and redaction checks
• document the 2048 launch asset path and update current status/install docs

Verification

• cargo fmt --check
• cargo test --lib -- --test-threads=1
• bash -n docs/demo/record-2048-demo.sh
• docs/demo/record-2048-demo.sh --dry-run
• docs/demo/record-2048-demo.sh --redaction-self-test
• node scripts/check-secrets.js
• git diff --check
• cargo run --quiet -- config provider list
• cargo run --quiet -- config model list
• cargo run --quiet -- config provider show
• cargo run --quiet -- quickstart --json

[github-actions]

DeepSeekCode review of PR #30 (Improve first-run config and add 2048 demo recorder)

Let me fetch the PR diff from the remote branch.

[chatgpt-codex-connector]

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