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.

.tfcode/command/commit.md

@@ -0,0 +1,37 @@
+---
+description: git commit and push
+model: opencode/kimi-k2.5
+subtask: true
+---
+
+commit and push
+
+make sure it includes a prefix like
+docs:
+tui:
+core:
+ci:
+ignore:
+wip:
+
+For anything in the packages/web use the docs: prefix.
+
+prefer to explain WHY something was done from an end user perspective instead of
+WHAT was done.
+
+do not do generic messages like "improved agent experience" be very specific
+about what user facing changes were made
+
+if there are conflicts DO NOT FIX THEM. notify me and I will fix them
+
+## GIT DIFF
+
+!`git diff`
+
+## GIT DIFF --cached
+
+!`git diff --cached`
+
+## GIT STATUS --short
+
+!`git status --short`