Add GITHUB_NOTIFY_CHAT_ID to make config prompts

[dcellison]

Summary

Add GITHUB_NOTIFY_CHAT_ID to the interactive make config prompts so it persists in install.conf and survives make apply.

Without this, the env var had to be manually added to /etc/kai/env, where it would be silently dropped on the next make apply (which regenerates the env file from install.conf).

Changes

Change	Detail
_validate_chat_id()	New validator accepting any non-zero integer (Telegram group IDs are negative)
_cmd_config() prompt	New "GitHub notifications" section between issue triage and optional features
Env dict entry	GITHUB_NOTIFY_CHAT_ID added to env dict when non-empty
Test update	test_writes_install_conf input list updated for new prompt

Test plan

• test_writes_install_conf updated with new prompt input
• test_reads_existing_defaults passes (empty default accepted)
• All 1147 tests pass, make check clean
• Manual: run make config, enter a group chat ID, verify it appears in install.conf

Fixes #183

[dcellison]

Review by Kai

This is a clean, focused PR. No critical issues or bugs found.

One minor suggestion:

install.py:176 — _validate_chat_id only catches ValueError, but that's actually correct here: int() on a string raises only ValueError for non-numeric input (no OverflowError risk since Python's int() handles arbitrary precision). No issue.

Suggestion (low priority): tests/test_install.py:294 — The test only exercises the empty/disabled path. A second test case with a valid negative group ID (e.g., "-1001234567890") and one with "0" (should loop/reject) would give fuller coverage of _validate_chat_id. Not a blocker.

Everything else looks correct:

• Validator correctly accepts any non-zero integer, including negative Telegram group IDs
• Loop logic properly accepts empty (feature disabled) or valid ID
• Env dict only populated when non-empty
• Placement in the prompt sequence matches the PR description
• No injection risk (integer string stored in a config file)

Ready to merge.

[dcellison]

Review by Kai

The PR is clean. The prior review's suggestion about _validate_chat_id test coverage has been addressed — the new assertions in test_validates_required_fields (lines 354-357) cover negative IDs, positive IDs, zero, and non-numeric strings.

No new issues to raise:

• Validator (install.py:176): Correct. int() handles the full valid range; empty-string case is handled at the call site, not inside the validator.
• Prompt loop (install.py:382): Pattern is consistent with the rest of _cmd_config. Empty accepted, non-zero integer accepted, anything else re-prompts.
• Env dict (install.py:448): Guarded by if github_notify_chat_id — the "0"-rejection in the validator means a zero ID can never reach this point, but the guard is still correct on its own terms.
• Test input list (tests/test_install.py:294): Position of the new "" entry matches the new prompt's position in the function.

Ready to merge.