Remove marketing/ directory (51 files) and 19 unused asset files
that are not referenced in README.md from git tracking. Update
.gitignore to prevent re-adding them.
Only the 17 SVGs actually used in README are now tracked in assets/.
## Claude Code integration now fully opt-in (Fix 3)
- `pbi connect` no longer writes to ~/.claude/ automatically
- New `pbi-cli` entry point: `pbi-cli skills install/uninstall/list`
- `pbi-cli skills install` shows exact paths before writing and requires y/N confirmation
- `pbi connect` prints a one-line tip if skills are not yet installed
- `pbi skills` subgroup removed from the `pbi` entry point
## DLL licensing compliance (Fix 1)
- pyproject.toml updated to PEP 639 SPDX dual expression:
MIT AND LicenseRef-Microsoft-AS-Client-Libraries
- license-files declaration: LICENSE, THIRD_PARTY_LICENSES.md, NOTICE
- THIRD_PARTY_LICENSES.md: full verbatim MS Analysis Services Client Libraries EULA
- NOTICE: short-form attribution for wheel redistribution
- src/pbi_cli/dlls/README.md: in-directory sentinel for the MS DLLs
- setuptools requirement bumped to >=77.0 for PEP 639 support
## SECURITY.md rewrite (Fix 2)
- Supported versions table updated to 3.10.x
- Architecture section: no MCP server, no subprocess, direct pythonnet interop
- Global Configuration Modifications section updated to reflect opt-in model
- Bundled Binaries section references THIRD_PARTY_LICENSES.md
## Documentation
- README.md, README.pypi.md: corrected 3-step setup flow
- CHANGELOG.md: [3.10.3] entry
- CONTRIBUTING.md: pbi skills -> pbi-cli skills
- All 7 semantic model SKILL.md files: prerequisites updated to 3-step flow
- New SVG/PNG marketing and documentation assets
