Merge #7295: fix: read governance debug log tail in binary mode

0293c6d fix: read governance debug log tail in binary mode (PastaClaw)

Pull request description:

  # Summary

  - fix `feature_governance_cl.py` log tail polling to seek `debug.log`
    in binary mode
  - decode the tailed bytes after reading so the seek offset stays valid
    for the stream mode
  - preserve the existing behavior of scanning only the last 100 KiB for
    the expected governance tip message

  ## Context

  This is a follow-up for a valid review finding from merged PR #7258:
  <#7258 (comment)>

  Upstream `develop` currently opens `debug.log` in text mode but computes
  the seek position with a binary offset. The final fix here uses a fully
  binary tail read and decodes afterward, which avoids both mixed-mode seek
  problems and text-stream offset arithmetic.

  ## Validation

  - `python3 -m py_compile test/functional/feature_governance_cl.py`
  - pre-PR code review gate verdict: `ship`

  I did not run `feature_governance_cl.py` end-to-end because this worktree
  does not have built `dashd`/test binaries available, and building Dash
  Core would be disproportionate for this narrowly scoped Python
  functional-test fix.

Top commit has no ACKs.

Tree-SHA512: 0f5f4837da1657e35a370e8591a4438c610084ce8f9b277be9e20c7318d48d86ada3c4a78b3e8182a5b61797bd72344addc9e07503581c7095ecb55e17aa8c5b

Author: PastaPastaPasta

test/functional/feature_governance_cl.py

@@ -147,10 +147,10 @@ def run_test(self):
         expected_msg = f'CGovernanceManager::UpdatedBlockTip -- nCachedBlockHeight: {tip_height}'
 
         def governance_tip_updated(node):
-            with open(node.debug_log_path, encoding='utf-8') as dl:
+            with open(node.debug_log_path, "rb") as dl:
                 seek_pos = node.debug_log_size(mode="rb") - 100 * 1024  # read the last 100 KiB only
                 dl.seek(seek_pos if seek_pos > 0 else 0)
-                debug_log_part = dl.read()
+                debug_log_part = dl.read().decode("utf-8", errors="replace")
             return expected_msg in debug_log_part
 
         for node in self.nodes[0:5]: