merge: resolve 0.7.7 conflicts with master (Release/0.7.6 #35)

Conflict resolution between release/0.7.7 (T4 per-call context for
/gate) and origin/master (Release/0.7.6 #35, which bumped the SDK
to 0.7.6):

* pyproject.toml: keep 0.7.7 (the HEAD side). 0.7.6 on master is
  superseded by 0.7.7 once this merges.
* CHANGELOG.md: keep BOTH the new 0.7.7 block (from HEAD) and the
  0.7.6 block (from master). They document different releases and
  are listed in chronological order with the older 0.7.6 block below.
* src/nullrun/{__init__.py, runtime.py, transport.py}: auto-merged
  cleanly - master doesn't touch the T4 hunks.

Auto-merge result equals HEAD, but the merge commit is still
needed to record the parent relationship and clear the conflict
state on the PR.

Author: maltsev-dev

src/nullrun/__version__.py

@@ -1,4 +1,4 @@
 """NullRun Platform SDK."""
 
-__version__ = "0.7.6"
+__version__ = "0.7.7"
 __platform_version__ = "1.0.0"