fix: skills, dbt-tools, and altimate-setup not bundled in shipped npm binary

[anandgupta42]

Problem

Several packages and skills are not getting bundled when shipping the npm binary:

1. altimate-setup skill missing — exists in packages/opencode/.opencode/skills/ but publish.ts copies from root .opencode/skills/, so it never ships
2. @altimateai/dbt-tools not shipped — not a dependency, not built in release workflow, not copied into dist
3. Skills unavailable for Homebrew/AUR/Docker — these channels skip npm postinstall, so no skills at all
4. Two separate skills directories (root vs packages/opencode) cause split-brain

Solution

• Embed skills in binary at build time (like migrations) with filesystem-first fallback
• Consolidate altimate-setup to root .opencode/skills/
• Bundle dbt-tools binary+dist in npm package with postinstall symlinking
• Export ALTIMATE_BIN_DIR from wrapper scripts, prepend to PATH in bash tool
• Handle Windows .cmd shim, copy fallback path resolution, and builtin: location prefix in skill tool

Related: #308