refactor: apply minimal tfcode branding

- Rename packages/opencode → packages/tfcode (directory only)
- Rename bin/opencode → bin/tfcode (CLI binary)
- Rename .opencode → .tfcode (config directory)
- Update package.json name and bin field
- Update config directory path references (.tfcode)
- Keep internal code references as 'opencode' for easy upstream sync
- Keep @opencode-ai/* workspace package names

This minimal branding approach allows clean merges from upstream
opencode repository while providing tfcode branding for users.

packages/tfcode/BUN_SHELL_MIGRATION_PLAN.md

@@ -0,0 +1,136 @@
+# Bun shell migration plan
+
+Practical phased replacement of Bun `$` calls.
+
+## Goal
+
+Replace runtime Bun shell template-tag usage in `packages/opencode/src` with a unified `Process` API in `util/process.ts`.
+
+Keep behavior stable while improving safety, testability, and observability.
+
+Current baseline from audit:
+
+- 143 runtime command invocations across 17 files
+- 84 are git commands
+- Largest hotspots:
+  - `src/cli/cmd/github.ts` (33)
+  - `src/worktree/index.ts` (22)
+  - `src/lsp/server.ts` (21)
+  - `src/installation/index.ts` (20)
+  - `src/snapshot/index.ts` (18)
+
+## Decisions
+
+- Extend `src/util/process.ts` (do not create a separate exec module).
+- Proceed with phased migration for both git and non-git paths.
+- Keep plugin `$` compatibility in 1.x and remove in 2.0.
+
+## Non-goals
+
+- Do not remove plugin `$` compatibility in this effort.
+- Do not redesign command semantics beyond what is needed to preserve behavior.
+
+## Constraints
+
+- Keep migration phased, not big-bang.
+- Minimize behavioral drift.
+- Keep these explicit shell-only exceptions:
+  - `src/session/prompt.ts` raw command execution
+  - worktree start scripts in `src/worktree/index.ts`
+
+## Process API proposal (`src/util/process.ts`)
+
+Add higher-level wrappers on top of current spawn support.
+
+Core methods:
+
+- `Process.run(cmd, opts)`
+- `Process.text(cmd, opts)`
+- `Process.lines(cmd, opts)`
+- `Process.status(cmd, opts)`
+- `Process.shell(command, opts)` for intentional shell execution
+
+Git helpers:
+
+- `Process.git(args, opts)`
+- `Process.gitText(args, opts)`
+
+Shared options:
+
+- `cwd`, `env`, `stdin`, `stdout`, `stderr`, `abort`, `timeout`, `kill`
+- `allowFailure` / non-throw mode
+- optional redaction + trace metadata
+
+Standard result shape:
+
+- `code`, `stdout`, `stderr`, `duration_ms`, `cmd`
+- helpers like `text()` and `arrayBuffer()` where useful
+
+## Phased rollout
+
+### Phase 0: Foundation
+
+- Implement Process wrappers in `src/util/process.ts`.
+- Refactor `src/util/git.ts` to use Process only.
+- Add tests for exit handling, timeout, abort, and output capture.
+
+### Phase 1: High-impact hotspots
+
+Migrate these first:
+
+- `src/cli/cmd/github.ts`
+- `src/worktree/index.ts`
+- `src/lsp/server.ts`
+- `src/installation/index.ts`
+- `src/snapshot/index.ts`
+
+Within each file, migrate git paths first where applicable.
+
+### Phase 2: Remaining git-heavy files
+
+Migrate git-centric call sites to `Process.git*` helpers:
+
+- `src/file/index.ts`
+- `src/project/vcs.ts`
+- `src/file/watcher.ts`
+- `src/storage/storage.ts`
+- `src/cli/cmd/pr.ts`
+
+### Phase 3: Remaining non-git files
+
+Migrate residual non-git usages:
+
+- `src/cli/cmd/tui/util/clipboard.ts`
+- `src/util/archive.ts`
+- `src/file/ripgrep.ts`
+- `src/tool/bash.ts`
+- `src/cli/cmd/uninstall.ts`
+
+### Phase 4: Stabilize
+
+- Remove dead wrappers and one-off patterns.
+- Keep plugin `$` compatibility isolated and documented as temporary.
+- Create linked 2.0 task for plugin `$` removal.
+
+## Validation strategy
+
+- Unit tests for new `Process` methods and options.
+- Integration tests on hotspot modules.
+- Smoke tests for install, snapshot, worktree, and GitHub flows.
+- Regression checks for output parsing behavior.
+
+## Risk mitigation
+
+- File-by-file PRs with small diffs.
+- Preserve behavior first, simplify second.
+- Keep shell-only exceptions explicit and documented.
+- Add consistent error shaping and logging at Process layer.
+
+## Definition of done
+
+- Runtime Bun `$` usage in `packages/opencode/src` is removed except:
+  - approved shell-only exceptions
+  - temporary plugin compatibility path (1.x)
+- Git paths use `Process.git*` consistently.
+- CI and targeted smoke tests pass.
+- 2.0 issue exists for plugin `$` removal.