Support mixed identity webhook subscriptions across SDKs and CLI

[dimavrem22]

Executive Summary

Support identity-owned subscriptions combining notification events across email, SMS, iMessage, calls, and A2A in the Python, TypeScript, and Rust SDKs and CLI.

Description

Accept mixed notification families under a canonical identity while retaining mutually exclusive legacy owner inputs. Subscription revision enables optional conditional update/delete, and event-list updates keep full-replacement semantics.

Delivery history exposes canonical targets and replay availability without losing original subscription IDs. Examples, reference docs, bundled skills, and release versions are updated to 0.7.2.

Reason

A subscription should follow an identity across channel provisioning changes. Clients also need a revision precondition to safely preserve concurrent event selections during reconciliation.

Decisions

• Keep existing public method signatures and legacy response parsing compatible. Rust conditional operations use additive helpers.
• Incoming-call actions remain separate synchronous call-control configuration.
• All existing notification types are allowed; this does not automatically select every event.
• Server validation remains authoritative for exact event membership. No wildcard subscription behavior is added.
• Release order: Publish 0.7.2 only after the compatible API is available; publish the TypeScript SDK before the CLI. The existing 0.7.1 release already includes custom signatures and remains unchanged.
• Rollout: No consolidation job is planned. Installed plugins may keep their existing separate event-family subscriptions; upgrading them is not a prerequisite for the ownership migration.

Testing

• Python: 1,127 passed, 3 skipped; Ruff passed.
• TypeScript: 1,126 passed, 3 skipped; build and packed-bundle verification passed.
• CLI: 150 passed, including actual local HTTP create/update/delete wire requests.
• Rust: 357 unit tests and 3 doctests passed, 1 doctest ignored; all-target/all-feature Clippy with warnings denied passed.
• Python wheel/sdist and npm tarball reproduced byte-for-byte across two builds; the TypeScript packed-bundle check passed. No live API calls or deployments.
• Rebased onto 8bafc65d after custom-signature support shipped as 0.7.1; the suites above cover both signature and webhook APIs at b5667e7e. Existing signature code, skill examples, and changelog history are preserved. Bundled Codex skills advance to plugin version 0.1.7.
• Exercise webhooks.subscriptions.create with mixed identity events, update/delete with an expected revision, and delivery-history parsing: mixed selections are accepted, stale writes return the API conflict, and original history IDs remain available.
• Hosted CI at this head: Python, TypeScript, Rust, CLI, plugin validation, and notification-format tests passed; Rust CodeQL analysis is still running. Live integration jobs are skipped while this PR is draft.

This PR remains draft; live integration testing and package publication are separate, unperformed steps.

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