release: v1.2.0 — Tool-Boundary Guardrails Complete & Structured Synthesis Follow-ups

[johnnichev]

Bumps version 1.1.0 → 1.2.0 and rolls the [Unreleased] changelog into a dated [1.2.0] section (both changelog files).

Contents already merged:

• feat: run guardrails over tool return values (opt-in tool_results stage) #168 — tool_results guardrail stage with contain-record-raise block semantics + cache-hit guarding (closes Add a tool_results guardrail stage (gate tool return values, symmetric with tool_args #160) #165)
• feat: conditional/single-pass structured synthesis + explicit validation outcome #169 — conditional/single-pass structured synthesis, conservative reuse gate, structured_status/structured_error (closes Structured output (final_turn_only): make the synthesis call conditional + expose validation outcome (follow-up to #162) #164, Structured output in a single pass with tools (skip the extra synthesis call when provider supports tools+json_schema) #166)
• feat: observer events for guardrail trips (on_guardrail_triggered) #170 — on_guardrail_triggered observer events with trip fidelity + async block delivery (closes Observability for guardrail trips and structured-output validation (observer/trace events) #167)

All additive; frozen 1.0 API unchanged. After merge: tag v1.2.0 → publish CI uploads to PyPI; GitHub Release created manually.

https://claude.ai/code/session_01L1JWChKMs9yTyK92qquhJa