chore(release): prepare 2.8.0 - #300

Prepare version 2.8.0 across all seven published packages and nine first-party Skill metadata files.

• Consolidate the unreleased 2.7.3 changelog draft into bilingual 2.8.0 notes, covering changes since the latest stable release, 2.7.2.
• Describe user-facing changes: Aliyun CLI integration, AK/SK-based Console tokens, custom model import, output and quiet behavior, credential precedence, model recommendations, and related fixes.
• Keep README files unchanged and omit architecture and internal-library details from the release notes.

Validation:

• Fresh vp check: passed with 0 errors and 2 existing warnings.
• Channel and stable dry-runs passed on the exact file contents in this commit, including builds, packing, publint, and gitleaks for all seven packages.
• Verified all package and Skill versions are 2.8.0 and git diff --check passes.

Dry-runs did not compile the cross-platform binary matrix; OSS upload checks were skipped because the local FC configuration is absent. No publication workflow has been dispatched.