feat: budget alerts and tiered degradation (#83, #84) (#115)

* feat: momentum tracking and hype risk calibration (#81, #82) - Add scripts/momentum_tracker.py: tracks press-correlated repo star trajectory at week +2 and +4, classifies as sustained/faded, updates predictions.jsonl validated field - Add scripts/calibrate_hype_risk.py: reads momentum data, compares hype risk predictions vs actuals, outputs calibration report with recommended threshold adjustments - Add tests/test_momentum_tracker.py: 42 tests covering both scripts Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com> * feat: budget alerts and tiered degradation (#83, #84) - budget_alerts.py: evaluates run cost and monthly spend against thresholds, emits GitHub Actions annotations, exits 1 only on hard $1.00 cap - tier_selector.py: selects service tier (normal/budget/minimal/emergency) based on cost estimates and monthly spend, outputs JSON config - Tests for both scripts (28 tests) Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com> --------- Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>