refactor(memory): disable tool/skill extraction and retire compressor V2

[chenjw]

Description

Temporarily disable ordinary tools and skills memory extraction, make SessionCompressorV3 the only session extraction implementation, and remove SessionCompressorV2.

V3 now owns the prepared extraction context, memory-type whitelist initialization, public error behavior, and extraction telemetry. Trajectory, experience, and optional executable session-skill training remain case-driven: when ordinary extraction produces no case, none of those artifacts are trained.

Human Involvement

• A human participated in the implementation or review loop
• This PR was generated entirely by AI agents without human participation in the loop

Related Issue

Fixes #3292

Type of Change

• Bug fix (non-breaking change that fixes an issue)
• New feature (non-breaking change that adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• Documentation update
• Refactoring (no functional changes)
• Performance improvement
• Test update

Changes Made

• Set the ordinary tools.yaml and skills.yaml memory schemas to enabled: false while retaining disabled-schema introspection.
• Route session and service extraction exclusively through SessionCompressorV3.extract_long_term_memories() and preserve case-driven trajectory/experience/executable-skill training.
• Restore V3 extraction-context preparation, allowed-type initialization, error contracts, and telemetry previously covered by V2.
• Delete SessionCompressorV2, its lock-only configuration, and V2-only tests; migrate reusable coverage to V3/shared components.
• Update active English, Chinese, design, and example documentation for the V3-only flow.

The V2 deletion intentionally does not provide an import compatibility alias, so external imports of openviking.session.compressor_v2 will fail.

Testing

• I have added tests that prove my fix is effective or that my feature works
• New and existing unit tests pass locally with my changes
• I have tested this on the following platforms:
  • Linux
  • macOS
  • Windows

Focused verification on the final branch:

• 68 passed for V3 extraction, registry disablement, memory diff/config coverage, and V3-only session routing.
• Ruff checks for all changed Python files pass.
• git diff --check origin/main...HEAD passes.

The broader adjacent server/memory suites are not fully green in the current local environment. Observed failures include an installed AGFS binding without glob_directory, background archive tasks exceeding the tests' 10-second timeout, and existing output-language expectation mismatches. This is why the PR is opened as Draft.

Checklist

• My code follows the project's coding style
• I have performed a self-review of my code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• My changes generate no new warnings
• Any dependent changes have been merged and published

Screenshots (if applicable)

Not applicable.

Additional Notes

The branch contains exactly two commits: one for temporarily disabling ordinary tool/skill extraction, and one for the V3 migration and V2 retirement.