Fix three command failures in Claude Code sandbox

[JohanLorenzo]

Summary

• init: The original flow ran pre-commit install before git commit --amend, so the amend fired the newly installed hooks (which tried to install sqlfluff via pip and failed with SSLCertVerificationError in the sandbox). Fix: move pre-commit autoupdate to before the initial commit so the updated config is included in that commit, then run pre-commit install only after all commits are done. The initial commit has no hooks installed; the amend is eliminated entirely. Also clear GIT_DIR/GIT_INDEX_FILE env vars inherited from a parent worktree, which caused git subprocesses during tests to operate on the wrong repo.
• update: Pre-check ~/.cargo/ writability before invoking cargo. Replaces raw "Operation not permitted (os error 1)" with a single actionable message pointing the user outside the sandbox.
• execute --interactive: Detect no-TTY via std::io::IsTerminal. When --interactive is requested without a terminal: use the parameter's declared default value if one exists; otherwise bail with an explicit --param name=<value> hint instead of crashing with IO error: not a terminal.

Verification

498bc5d — Reorder init to eliminate git commit --amend and clear git env vars

Before:

Error: git commit --amend failed: ... SSLError(SSLCertVerificationError('OSStatus -26276'))

After:

⚙ Setting up pre-commit...
  ⚠ pre-commit autoupdate failed, using template versions
⚙ Initializing git repository...
⚙ Creating initial commit...
  ✓ Initial commit created
⚙ Installing pre-commit hooks...
  ✓ Installed pre-commit git hooks
✓ Repository scaffolded successfully
exit: 0

458ac1a — Detect ~/.cargo/ write restriction in update command

Before:

ERROR Fatal error:
  × failed to parse binstall crates-v1 manifest: I/O Error: Operation not permitted (os error 1)
cargo binstall not available, falling back to cargo install
error: failed to open: /Users/.../.cargo/.crates.toml
Caused by: Operation not permitted (os error 1)
Error: cargo install stmo-cli failed
exit: 1

After:

Error: Cannot update stmo-cli in the current environment (write access to ~/.cargo/ is restricted).
Run this command outside the sandbox:
  cargo binstall stmo-cli
exit: 1

34257a7 — Fall back to defaults in execute --interactive when no TTY

Before (any parameterized query):

Error: IO error: not a terminal
exit: 1

After (param has no default):

Error: No TTY available for interactive prompt. Supply parameter explicitly: --param my_param=<value>
exit: 1

After (param has a default):

Parameters:
  my_param = "default_val"
[proceeds to execute query]
exit: 0