Add opt-in Xquik search and fix context compression

[kriptoburak]

Summary

• Fix context compression so configured primer and recent messages stay intact. Only the middle history is summarized.
• Version the Temporal change. Existing version 1 histories keep their prior request shape and 20-message behavior.
• Propagate tenant identity for new summary embeddings. Clamp compression targets to the Python service contract.
• Add an operator-gated xquik_search tool for paid public X reads.
• Keep Xquik disabled by default, marked dangerous, and excluded from automatic selection.
• Validate filters and dates. Normalize the Xquik response contract and sanitize upstream errors.
• Document opt-in configuration, paid scope, safe limits, and independence wording.

Fixes #190

Xquik Safety

• Registration requires XQUIK_SEARCH_ENABLED=true.
• Requests use the fixed https://xquik.com/api/v1/x/tweets/search endpoint.
• Authentication uses x-api-key. Responses opt into the 2026-04-29 normalized contract.
• Each call is a paid read. Smaller limits reduce paid scope.
• A 402 response never creates a checkout or top-up.
• Raw upstream errors never reach tool output. Returned post content is labeled untrusted.

Validation

• go test -short -race ./internal/activities ./internal/workflows ./internal/workflows/strategies
• go build ./...
• Focused Python tests: 12 passed
• Full Python suite: 889 passed, 31 failed, 9 errors, 2 skipped
• Exact base suite: 877 passed, 31 failed, 9 errors, 2 skipped
• The branch adds 12 passes. The failing and erroring test list matches the base exactly.
• Targeted Ruff checks passed. The repository-wide optional BrowserTool F401 remains unchanged from the base.
• Both Compose files parsed with all 4 Xquik variables.
• git diff --check
• Rust was unchanged. cargo fmt --check still reports existing formatting drift in unchanged Rust files.

[kriptoburak]

I rebuilt this PR on the current main branch and replaced the old head with signed commit 43cb55b.

The branch now fixes #190 as the independent repository issue and adds the Xquik integration as an explicit, disabled-by-default paid tool. Focused Python tests pass 12/12, the race-tested Go packages pass, and go build ./... passes. The full Python suite adds 12 passes with the same baseline failure and fixture-error list.

GitHub CI is waiting for fork-workflow approval and created zero jobs: https://github.com/Kocoro-lab/Shannon/actions/runs/30520600651