feat: cast init interactive menu + dashboard parse-error fix

[shenxianpeng]

Summary

• cast init interactive type selection: when project type detection fails in a TTY, show a numbered menu instead of exiting. Non-TTY/CI keeps the existing exit-1 behavior.
• Dashboard parse-error fix: parse_sarif() now returns an ERROR dict instead of None on JSON/IO failure. Failed files show as a visible PARSE ERR row (amber) in the dashboard table. The compliance banner shows PARSE ERRORS instead of the misleading ALL CLEAR when unresolved parse failures exist.

Changes

File	What changed
src/cast_cli/main.py	Add import sys, _prompt_type_selection() helper, TTY-aware branch in init
dashboard/generate.py	parse_sarif() returns error dict; generate_dashboard() includes error rows; render_badge/render_table/render_compliance_banner handle ERROR status
dashboard/template.html	CSS: --error-row-bg, .row-error, .badge.error, .parse-error-msg, .compliance-banner.has-parse-errors
tests/test_dashboard.py	Update 2 tests to match new behavior

Test plan

• All 65 tests pass (pytest tests/ -v)
• cast init in a TTY with no project markers shows numbered menu
• cast init in CI (non-TTY) with no project markers exits 1 with instructions
• cast init --type go still works as before
• Dashboard with a malformed SARIF shows PARSE ERR row, not ALL CLEAR
• Dashboard with both a valid SARIF and a bad SARIF shows both rows correctly

https://claude.ai/code/session_01PovvcUbam7c1xDTrEPRhT7