fix(plugins): add explicit encoding to read_text/write_text in plugins/

[AlexFucuson9]

Summary

Add encoding="utf-8" to all read_text()/write_text() calls in plugins/ directory.

Path.read_text() defaults to system locale (cp1252 on Windows), causing UnicodeDecodeError for UTF-8 content. Ruff rule PLW1514.

Files fixed

• Platform adapters: slack, discord, telegram, feishu, whatsapp, google_chat
• Memory plugins: mem0, hindsight, honcho
• Other: disk-cleanup, google_meet, hermes-achievements

Test plan

• python3 -m py_compile passes for all files
• All unencoded calls fixed

[alt-glitch]

This was generated by AI during triage.

Related: #50689 (your broader open fix(plugins,scripts) encoding rollout). 12 of the 13 plugin files changed here are an exact subset of #50689; the only file unique to this PR is plugins/memory/mem0/_setup.py. Not a duplicate (subset of the broader PR), but reviewers may prefer to fold the one extra file into #50689 and close this, or merge this and drop the overlap from #50689 — to avoid conflicting edits to the same lines.

[tonydwb]

Code Review Summary

Verdict: Approved

Adds explicit encoding="utf-8" to read_text/write_text calls in the plugins/ directory (13 files, 34 additions). Consistent with the encoding fix pattern applied across the codebase. Well-scoped, no side effects.

---

Reviewed by Hermes Agent