Bump `trio` minimum for ctx cancellation reasons

Require `trio>=0.34.0`, the version exercised with object-valued
`Cancelled.reason` payloads in the downstream ctx experiment.

Resolve `uv.lock` with `trio` at `0.34.0`; also synchronize the
existing `py-multibase` requirement. No other package version moves.

Prompt-IO: ai/prompt-io/opencode/20260919_trio_reason_minimum.md

(this patch was generated in some part by `opencode` using
`gpt-6-astra` (`openai`))

ai/prompt-io/opencode/20260919_trio_reason_minimum.md

@@ -0,0 +1,38 @@
+---
+model: openai/gpt-6-astra
+service: opencode
+scope: config
+substantive: true
+git_ref: dd758da5
+raw_file: 20260919_trio_reason_minimum.raw.md
+---
+
+## Prompt
+
+Build on the human's cancellation-reason/context-status prototype,
+keeping the minimum Trio version bump separate from context changes.
+
+## Response summary
+
+Require Trio >=0.34.0, the installed version whose object-valued
+cancellation-reason behavior was inspected and exercised. Update the
+lock with uv lock --upgrade-package trio==0.34.0. The initial offline
+attempt could not resolve uncached registry metadata; normal resolution
+updated Trio alone as a package version, also synchronizing an existing
+py-multibase requirement in lock metadata. No environment was synced.
+
+## Files changed
+
+- pyproject.toml: Trio minimum and explanatory dependency comment.
+- uv.lock: Trio package metadata and project requirement synchronization.
+
+## Human contributions
+
+The human proposed a downstream experiment, explicitly accepted the
+implementation-dependent nature of non-string reason payloads, and
+required the dependency bump and context code to be separate commits.
+
+## Limit
+
+The minimum selects a verified implementation. It does not turn arbitrary
+object reasons into a documented stable Trio public contract.

ai/prompt-io/opencode/20260919_trio_reason_minimum.raw.md

@@ -0,0 +1,12 @@
+---
+model: openai/gpt-6-astra
+service: opencode
+git_ref: dd758da5
+diff_cmd: git diff HEAD
+---
+
+> git diff HEAD -- pyproject.toml uv.lock
+
+Set trio>=0.34.0 and resolve the Trio package at 0.34.0 separately from
+the subsequent context-status implementation. No installed packages
+were changed. The working lock has a ten-line diff.

pyproject.toml

@@ -39,7 +39,9 @@ dependencies = [
   # https://packaging.python.org/en/latest/discussions/install-requires-vs-requirements/#id5
   # TODO, for 3.13 we must go go `0.27` which means we have to
   # disable strict egs or port to handling them internally!
-  "trio>0.27",
+  # Cancelled.reason carries context fault metadata; 0.34 is the
+  # minimum exercised by the object-valued reason regressions.
+  "trio>=0.34.0",
   "tricycle>=0.4.1,<0.5",
   "wrapt>=1.16.0,<2",
   "colorlog>=6.8.2,<7",