fix(wecom): pad aeskey before base64 decode to handle unpadded WeCom keys

[elephantjohn]

WeCom delivers aeskey as 43-char base64 strings without trailing '='
padding. Calling base64.b64decode() on it directly raises
binascii.Error: 'Incorrect padding', causing image/file decryption
to fail silently — users see no response when sending images.

Fix: append '=' chars to make the length a multiple of 4 before
decoding, which is the standard workaround for unpadded base64.

What does this PR do?

Related Issue

Fixes #

Type of Change

• 🐛 Bug fix (non-breaking change that fixes an issue)
• ✨ New feature (non-breaking change that adds functionality)
• 🔒 Security fix
• 📝 Documentation update
• ✅ Tests (adding or improving test coverage)
• ♻️ Refactor (no behavior change)
• 🎯 New skill (bundled or hub)

Changes Made

How to Test

Checklist

Code

• I've read the Contributing Guide
• My commit messages follow Conventional Commits (fix(scope):, feat(scope):, etc.)
• I searched for existing PRs to make sure this isn't a duplicate
• My PR contains only changes related to this fix/feature (no unrelated commits)
• I've run pytest tests/ -q and all tests pass
• I've added tests for my changes (required for bug fixes, strongly encouraged for features)
• I've tested on my platform:

Documentation & Housekeeping

• I've updated relevant documentation (README, docs/, docstrings) — or N/A
• I've updated cli-config.yaml.example if I added/changed config keys — or N/A
• I've updated CONTRIBUTING.md or AGENTS.md if I changed architecture or workflows — or N/A
• I've considered cross-platform impact (Windows, macOS) per the compatibility guide — or N/A
• I've updated tool descriptions/schemas if I changed tool behavior — or N/A

For New Skills

• This skill is broadly useful to most users (if bundled) — see Contributing Guide
• SKILL.md follows the standard format (frontmatter, trigger conditions, steps, pitfalls)
• No external dependencies that aren't already available (prefer stdlib, curl, existing Hermes tools)
• I've tested the skill end-to-end: hermes --toolsets skills -q "Use the X skill to do Y"

Screenshots / Logs

[alt-glitch]

Likely duplicate of #14580 — same root cause (WeCom 43-char unpadded base64 aeskey). See also #14888, #11899.

[alt-glitch]

Likely duplicate of #14580 — same root cause (WeCom 43-char unpadded base64 aeskey). See also #14888, #11899.

[teknium1]

This appears to be implemented on current main by the same WeCom AES-key padding fix.

Evidence from automated hermes-sweeper review:

• gateway/platforms/wecom.py:1046 pads aes_key to a multiple of four before base64.b64decode(...), which is the exact behavior requested here.
• The fix was added by 8f4c0bf0882c3c7258a65e3adade12d5b08068ea (fix(wecom): pad base64 AES key before decode).
• git tag --contains 8f4c0bf08 shows the fix is included in v2026.5.7 and later tags.
• The duplicate discussion from @alt-glitch points to the same root cause: WeCom 43-character unpadded base64 aeskey values.

Closing this PR as already implemented on main. Thanks for reporting and sending the focused fix.