Long project texts are cut to fit and saved to files, and failed saves no longer fall back to inline text

What

When a project is attached to a session, its name, description and instructions (prompt_template) are sent to the model. This release changes how long project texts are handled:

• Trimming (behind the tengu_proud_firefly flag, which has not been read): project name, description and prompt_template are cut to a size limit when they are too long. A note is added saying the project_info tool can provide a file holding the full text. Without the flag, the texts are sent whole.
• project_info files: project_info now writes a long description and instructions to a local_file, splitting long lines at 450 characters. It now builds name, description and instructions with a shared helper.
• Large project docs: reads of large project documents go to a local_file, and documents with very long lines are handled separately.
• No more inline fallback: if saving a project document to a file fails, the helper now returns a failure (not_stored or write_failed). Before, it returned the whole document inline. The warning now reads Projects tool: could not save a text of ${n} bytes to a file.
• Write guards: the tengu_lovely_rain and tengu_toasty_owl write guards are still behind flags. v2.1.310 built tengu_lovely_rain off by default; no reading has been taken for it under this release, and nothing has been read about tengu_toasty_owl.

Why

Large projects take up less of the conversation's working memory, and the model is told where to find the rest. Watch for large document reads that now fail outright where they used to arrive in full.