conformance: map signal step to public track_signal API (DEV-1201)

[devin-ai-integration]

Summary

Harness PR #47 activated the signal capability + added two experimental signal scenarios. This maps the harness signal step onto the Rust SDK's public signal surface and bumps the pinned harness ref. Driver-only; no SDK behavior change.

The SDK already exposes public Client::track_signal(Signal) (with Signal/SignalKind re-exported from the crate root), shipping event_id/signal_name/signal_type to signals/track with signal_type defaulting to "default". The driver's signal step was previously reported unsupported (exit 3); it is now implemented.

• conformance/src/main.rs: add signal to CAPABILITIES, add "signal" => step_signal dispatch arm (drops it from the unsupported fallthrough), add step_signal() mapping the step args onto Signal { event_id, name, kind←signal_type, sentiment, timestamp, properties, attachment_id, comment, after }.
• .github/workflows/conformance.yml: HARNESS_REF → cf744e9 (harness main, DEV-1201).

event_id/name are required (required_str); the rest map via the existing optional_str/properties/timestamp helpers, matching how the other steps are wired.

Verified locally (toolchain matching MSRV/stable): cargo build --manifest-path conformance/Cargo.toml clean, cargo fmt --check clean. Fault lane against the bumped corpus: signal-request-shape@fault → pass, runner exit 0. conformance/failures.txt unchanged — the other four experimental scenarios (hang-request-deadline, reconnect-identical-body, retry-500-then-200, retry-after-cap) are status: experimental (report-only) pre-existing gaps and do not gate.

Link to Devin session: https://app.devin.ai/sessions/c59705fa818b4a9ca7c51a24480064b1

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Note

Low Risk
Changes are limited to the conformance driver and CI harness pin; production SDK code is untouched.

Overview
The conformance driver now advertises and implements the harness signal capability instead of returning unsupported (exit 3). Harness scenarios that require signal can run against this SDK.

step_signal maps harness args onto public Client::track_signal (event_id, name, optional signal_type → kind, plus sentiment, timestamp, properties, attachment_id, comment, after). CI bumps the pinned raindrop-sdk-harness ref to the commit that activates signal scenarios.

No SDK behavior change — only the standalone conformance driver and workflow pin.

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[devin-ai-integration]

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[pavel-y-ivanov]

DEV-1201 pt3: signal step via public track_signal, conformance-only. CI green.