v0.18.3 -> v0.19.0

Summary

Introduces concurrent tool-call dispatch, an invoke_subagent in-process delegate, and a same-payload circuit breaker; switches search_web to the DuckDuckGo lite endpoint and hardens provider/fetch fallbacks across Codex, Google RSS, and Yahoo Finance.

Changes

FEAT

• Add three-pass concurrent tool-call dispatcher with Concurrent registry flag, fan-out for fetch_page/invoke_subagent/calculate, and per-batch stub activation guard
• Add invoke_subagent in-process sub-agent with isolated temp sessions, model/system-prompt/exclude overrides, and mandatory self-exclusion to prevent recursion
• Add same-payload retry circuit breaker across provider and tool calls to abort identical repeats after MaxRetry
• Expose ToolArgs on tool-call events so UIs can render arguments before execution

REFACTOR

• Switch search_web from html.duckduckgo.com to lite.duckduckgo.com/lite/ with new anchor/snippet parsing and drop sub-day time ranges unsupported by DDG
• Extract Yahoo Finance fetch constants and simplify tool registration layout

UPDATE

• Add prompt_cache_key (sha256 of system instructions) to Codex Responses API body to route identical prefixes to the same cache shard
• Allow Codex in general routing; separate system instructions for Responses API and abort repeated validator retries
• Consolidate tool cache storage and harden fetch fallbacks, including isRedirected404 detection for soft 404 via err=404/403/410 query params
• Harden Google RSS parameter handling with a default time range
• Strengthen agent tier routing and memory-driven tool recovery

Files Changed

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