`Actor.start_remote_task()` registers its caller context before
sending `Start`, but only cancellation cleaned that state.
Encoding, ack timeout, malformed ack and remote authorization
errors leaked it.
Protect the complete send, acknowledgement and validation phase.
Track successful publication, make a remote cancellation attempt
only when protocol-safe and always release the local context while
preserving the original startup error.
Cover both pre-publication serialization failure and a remote
`ModuleNotExposed` rejection without damaging a reused portal.
Caught-during: review remediation
Found-via: `/run-tests` startup-failure regressions
Review: PR #481 (opencode)
https://github.com/goodboy/tractor/pull/481#pullrequestreview-4956692120
Prompt-IO: ai/prompt-io/opencode/20260818T193004Z_bf06b4f8_prompt_io.md
(this patch was generated in some part by `opencode` using `gpt-5.6-sol` (`openai`))
Gud Boi