Why: With parallel tool execution the host-side tool wrapper can no
longer infer which invocation it is serving from a single in-flight
slot; tools need the call identity (ID/name/arguments) to pair process
state and per-call bookkeeping. Context injection keeps the tools
registry signature unchanged.
Evidence: go test ./... green; TestLoopToolSeesOwnCallInContext runs
two parallel calls and asserts each reads its own ID from ctx.
Impact: Additive WithToolCall/ToolCallFromContext helpers; runOne now
wraps the ctx before Execute. Callers that never inject keep ok=false
and are unaffected.
Refs: Dev task feature/agent-e1-parallel-fixes (F5 parallel wiring).
