fix(timeline): render events that are still encrypted and refresh on decryption

[eleboucher]

Description

messages in encrypted rooms didn't appear until you scrolled or refocused.

getType() returns m.room.encrypted until decryption finishes, but the render filter listed 'm.room.message.encrypted', which isn't a real type. b1ac4a6 turned that filter into a hard drop, so undecrypted events got no row, and nothing re-ran the filter once they decrypted.

also fixes messages that fail to decrypt showing nothing instead of the placeholder.

based on refactor/matrix-event-type-constants, which kept the bogus string as ROOM_MESSAGE_DECRYPTED. nothing sets that type, so it's removed.

Fixes #1553
Fixes #1508

Type of change

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• This change requires a documentation update

Checklist:

• My code follows the style guidelines of this project
• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• My changes generate no new warnings

AI disclosure:

• Partially AI assisted (clarify which code was AI assisted and briefly explain what it does).
• Fully AI generated (explain what all the generated code does in moderate detail).

[github-actions]

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