fix(cli): use bun in command hints

[kiyeonjeon21]

Summary

• Use the Studio package's bun dev script when hyperframes preview runs from the monorepo source path.
• Update stale CLI missing-build guidance from pnpm commands to bun commands.
• Leave release/packaging-related pnpm usage untouched, since that appears to be part of the publish workflow.

Why

I noticed a few user-facing CLI paths still referenced pnpm while checking the repo setup. CONTRIBUTING.md and AGENTS.md describe bun as the workspace package manager, so this keeps those small hints aligned with the documented development flow.

Validation

• bunx oxfmt --check packages/cli/src/commands/play.ts packages/cli/src/commands/preview.ts packages/cli/src/server/studioServer.ts
• bunx oxlint packages/cli/src/commands/play.ts packages/cli/src/commands/preview.ts packages/cli/src/server/studioServer.ts
• bun run --filter @hyperframes/cli typecheck
• bun run --filter @hyperframes/cli test -- src/server/studioServer.test.ts

[jrusso1020]

Verdict

Approve. Trivial, correct alignment of user-facing CLI hints with the documented bun-based workflow (CLAUDE.md:23 and AGENTS.md:65 both call out bun as the workspace package manager and explicitly say "NOT pnpm"). Each replacement is verified against the corresponding package.json script.

Verified:

• packages/studio/package.json defines "dev": "vite" → spawn("bun", ["run", "dev"]) is equivalent to the previous pnpm exec vite.
• packages/player/package.json defines "build": "tsup" → bun run --cwd packages/player build builds the player as expected.
• Root package.json defines "build" (orchestrates all packages) → bun run build is the correct root-level build.
• Author's stated scope is right: pnpm references in installerDetection.ts / autoUpdate.ts are correctly left alone — those detect end-user global installs and pnpm-installed users still need the pnpm add -g upgrade hint.

Key Concerns

(none)

Test Coverage

No test changes needed — these are message-string and command-name updates. The studioServer HTML snippet and the play/preview error paths are infrequent fallback branches; existing tests don't (and don't need to) snapshot the literal text.

Nits / Future

• packages/cli/src/commands/play.ts:28,36 and packages/cli/src/server/studioServer.ts:412 — bun run build is ambiguous about the working directory (it's a root-level script). The original pnpm build had the same ambiguity, so this isn't a regression, but contributor-facing hints could be made explicit, e.g. bun run build from the monorepo root or bun run --cwd <repo-root> build. Pure copy.
• packages/cli/src/commands/preview.ts:262 — runLocalStudioMode still spawns npx vite, which is intentional (this path runs against a user-installed @hyperframes/studio, not the monorepo) and consistent with using a universally available launcher. Just flagging that the pnpm→bun cleanup is correctly not extended here; no action needed.