fix(cli): roll back Bun 1.4

[marius-kilocode]

What Problem This Solves

The Bun 1.4 CLI toolchain introduced terminal startup regressions in v7.5.0. Subsequent prerelease runs also produced a blank linux-x64-baseline TUI artifact.

Why This Change Was Made

Restore the last proven release toolchain: Bun 1.3.14 with compiled code splitting disabled. This removes the Bun 1.4 runtime and type compatibility changes instead of adding more target-specific workarounds.

The temporary packaged-frame smoke changes from PRs #13472 and #13474 are also reverted so this PR contains one clean mitigation. Existing version, model snapshot, sandbox worker, and PTY release checks remain.

User Impact

The CLI returns to the runtime and compiled graph used by working v7.4.23. Compiled binaries are larger because entrypoints are not split.

Evidence

• Regenerated bun.lock with Bun 1.3.14; only @types/bun and bun-types changed.
• Core and CLI typechecks passed under the official Bun 1.3.14 executable.
• 14 PTY tests and 9 TUI worker tests passed under Bun 1.3.14.
• Built all 12 release targets under Bun 1.3.14, including normal and baseline variants.
• Native macOS arm64 standalone smoke checks passed.
• The compiled binary rendered the visible prompt from /Users/marius, where the v7.5.0 black screen was observed.
• Shared-file annotation and diff checks passed.

Failed prerelease runs:

• https://github.com/Kilo-Org/kilocode/actions/runs/32976503200
• https://github.com/Kilo-Org/kilocode/actions/runs/32980000469

[kilo-code-bot]

Code Review Summary

Status: No Issues Found | Recommendation: Merge

Files Reviewed (0 files)

No file changes since the previous review (empty chore: retrigger CI commit).

Previous Review Summaries (2 snapshots, latest commit cb4abf4)

Current summary above is authoritative. Previous snapshots are kept for context only.

Previous review (commit cb4abf4)

Status: No Issues Found | Recommendation: Merge

Files Reviewed (1 files)

• packages/opencode/script/build.ts

Previous review (commit 42a6366)

Status: No Issues Found | Recommendation: Merge

Files Reviewed (17 files)

• .changeset/restore-bun-runtime.md
• CONTRIBUTING.md
• bun.lock
• bunfig.toml
• nix/bun.nix
• package.json
• packages/containers/bun-node/Dockerfile
• packages/core/src/kilocode/pty/smoke.ts
• packages/core/test/kilocode/pty-durability.test.ts
• packages/core/test/kilocode/pty-smoke.test.ts
• packages/kilo-docs/pages/contributing/development-environment.md
• packages/kilo-vscode/docs/mercury-next-edit-testing.html
• packages/opencode/script/build.ts
• packages/opencode/script/kilocode/cli-smoke.ts
• packages/opencode/src/bun-compat.d.ts
• patches/@ff-labs%2Ffff-bun@0.9.4.patch
• script/upstream/package.json

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_{Review guidance: REVIEW.md from base branch main}

[WebReflection]

@marius-kilocode heads up, while updating dependencies due Dependabot security complains one of those trusted bun 1.4 was in. It probably got it due this PR previously merged but let's be sure CI is fully happy about it with latest PRs merged.