Problem

ECC still installs primarily by target and language. The repo now has first-pass selective-install manifests and a non-mutating plan resolver, but the installer itself does not yet consume those profiles.

Current groundwork already landed in-repo:

• manifests/install-modules.json
• manifests/install-profiles.json
• scripts/ci/validate-install-manifests.js
• scripts/lib/install-manifests.js
• scripts/install-plan.js

That means the missing step is no longer design discovery. The missing step is execution: wire profile/module resolution into the actual install flow while preserving backward compatibility.

Scope

Implement manifest-driven install execution for current ECC targets:

• claude
• cursor
• antigravity

Add first-pass support for:

• ecc-install --profile <name>
• ecc-install --modules <id,id,...>
• target-aware filtering based on module target support
• backward-compatible legacy language installs during rollout

Non-Goals

• Full uninstall/doctor/repair lifecycle in the same issue
• Codex/OpenCode install targets in the first pass if that blocks rollout
• Reorganizing the repository into separate published packages

Acceptance Criteria

• install.sh can resolve and install a named profile
• install.sh can resolve explicit module IDs
• Unsupported modules for a target are skipped or rejected deterministically
• Legacy language-based install mode still works
• Tests cover profile resolution and installer behavior
• Docs explain the new preferred profile/module install path