feat: add Special Situations SDK workflows

[daniel-scrivner]

Summary

• add a public client.situations namespace and flat Special Situations helpers
• support archive issues, details, filings, summary, Copy-for-LLM markdown export, feed, calendar, stats, performance, and form lookup
• preserve per-call retry/telemetry controls and add route/escaping regression coverage
• bump the Python SDK to 1.1.0 for the new public surface

Dependency

• archive issue helpers require datastream PR #1363 to be merged and deployed before production use

Validation

• python3 -m unittest discover -s tests
• python3 -m pytest -q
• git diff --check
• two-pass adversarial GPT-5.5 High review

Boundary

• public Special Situations only; no internal-only data capabilities are exposed

[daniel-scrivner]

Adversarial review record

• Pass 1 (GPT-5.5 High): accepted fixes for retry/telemetry controls being serialized into the URL and missing per-call controls on archive aliases.
• Pass 2 (GPT-5.5 High): accepted a 1.1.0 package-version bump for the new public namespace.
• Rejected feedback: none.
• The archive deployment dependency on datastream PR #1363 remains explicitly documented and release-gated.

[daniel-scrivner]

Underwriting-pack adversarial review record

• Pass 1 (GPT-5.5 High): accepted removal of unsupported response_mode and include query claims from docs and route assertions.
• Pass 2 (GPT-5.5 High): found the generic Python **params method still permitted those unsupported query parameters; accepted a strict signature that permits only client retry/telemetry controls, plus corrected retry tests.
• Rejected feedback: none.
• Verification: focused suites, full pytest, and diff hygiene passed.
• Dependency: this helper requires the API deployment containing datastream PR #1363.