twenty/v2.28.0: Revert AI chat chips to the [[kind:...:label]] syntax (#23852)

Removes the [[kind:…:label[[/kind]] closing-tag syntax and goes back to the simpler [[kind:…:label]] form for all four chip kinds (record, object, field, view). The parser is now a single regex pass instead of a two-pass scan with a per-reference closing-tag search, a legacy fallback and surplus-bracket handling. That removes 11 files.