fix: v1.7.1 patch — tier persistence, Ctrl-C guards, version string

[cody-rester]

Description

Patch release bundling three bug fixes found during a polish pass before shipping 1.7.1.

Type of Change

• Bug fix

Changes Made

• tier set persistence fix — when the active environment has its own tier field, the environment overlay (priority 3 in tier resolution) was silently overwriting any change made to config.json (priority 4) on every subsequent load. _persist_tier now propagates the new tier to the environment file when the env carries an explicit tier override. Also tightened the "already set" check to use ctx().tier (the effective resolved tier) rather than the raw config.json value.
• env edit Ctrl-C guards — the Gateway4 URI, username, and password prompts in handle_env_edit used bare if value: checks after .ask(). Pressing Ctrl-C returned None from questionary, which silently skipped the field and continued to the next prompt, trapping the user mid-flow. Each prompt now checks if value is None: raise KeyboardInterrupt.
• config init Ctrl-C guard — the "Create another environment?" loop used if not add_more: which treated a None return (Ctrl-C) as True, breaking the loop silently instead of raising. Added the explicit None check before the break.
• Version string — _version.py was still "1.7" from the 1.7.0 release; bumped to "1.7.1" so --version output matches the package.

Testing

• Manually reproduced the tier set persistence bug (env with tier: extended overlay, tier set standard appeared to succeed but tier show still showed extended). Verified fix resolves it.
• Ctrl-C behavior verified against the project pattern documented in CLAUDE.md.

Checklist

• Code follows the project's style guidelines
• Self-review of code has been performed
• Code has been commented where necessary
• Tested with make setup or relevant profile
• Commits follow conventional format (type: subject)
• No secrets or credentials committed
• Documentation has been updated accordingly
• PR has been labeled appropriately (enhancement, bug, documentation, refactor, chore)