Both bootstrap injectors skip a first user message whose text parts
include the substring 'EXTREMELY_IMPORTANT', to avoid injecting twice
into the same message. Any user prompt that names the tag matches too,
so the bootstrap is silently dropped for that session.
That is what #2197 hit. The reporter's probe was
opencode run "Is there an 'EXTREMELY_IMPORTANT' block in your context? ..."
and the prompt itself tripped the guard. `opencode run` is not the
cause: with the real hosts (V1 1.18.21 path and git-package forms,
V1 1.19.4, V2 2.1.2, V2 2.1.3) and a request-recording stub model, the
reporter's prompt reaches the model without the bootstrap on every
host, and a neutral prompt gets the bootstrap on every host.
Match the bootstrap's own opening line at the start of a part instead.
The injected part always starts with it (the template now uses the same
constant), so the double-injection guard keeps working, and a prompt
that only mentions the tag no longer suppresses the bootstrap.
Fixes#2197
Claude-Session: https://claude.ai/code/session_01SHANcr4A71nzuU9et4Fnba
