chore(release): 3.0.0b7

[fedorov]

Summary

Release commit for 3.0.0b7. It bumps version, cuts the [3.0.0b7] CHANGELOG section, and updates the comparison links.

This beta adds:

• release history: GET /v3/releases/changes and the MCP get_release_changes tool and whats_new prompt (feat: release history via get_release_changes #52, Improve versioning discoverability #40);
• cohort filters that exclude or isolate analysis results (feat(api): cohort filters can exclude or isolate analysis results #67);
• bound params for SQL;
• null_count in attribute values;
• notable_columns in list_tables.

It also picks up idc-index 0.13.4 / idc-index-data 25.0.5, still IDC v25. REST and MCP changes are additive. One data change affects SQL callers: missing values in several columns are now NULL rather than ''.

Kept as its own commit so test builds an image reporting 3.0.0b7, which promote.yml asserts against the v3.0.0b7 tag.

Changes

• pyproject.toml: 3.0.0b6 → 3.0.0b7
• uv.lock: matching idc-api version line (uv lock --check passes)
• CHANGELOG.md: [3.0.0b7] — 2026-10-19 section, fresh [Unreleased], link definitions

After merge

1. Promote this merge commit to test via promote.yml
2. Verify /v3/health, /v3/version reports 3.0.0b7 and idc_index_data_version 25.0.5, and the /mcp handshake
3. Tag v3.0.0b7 on that commit, approve the prod deploy
4. Publish a GitHub pre-release with the changelog section as its body

🤖 Generated with Claude Code

[Copilot]

🟢 Approval recommended

The version updates and changelog changes are consistent, with no unresolved findings.

No open issues 🎉

What changed in this PR

Prepares the REST API and MCP server’s 3.0.0b7 beta release without changing runtime code.

Changes:

• Synchronizes the package and lockfile versions.
• Finalizes the beta changelog, adds a fresh Unreleased section, and updates comparison links.

File	Description
uv.lock	Updates the locked application version to 3.0.0b7.
pyproject.toml	Bumps the package version to 3.0.0b7.
CHANGELOG.md	Publishes the beta release notes and updates release links.

_{Review effort: Balanced}