Make agent file writes append by default

README.md

@@ -290,7 +290,7 @@ GET /meetings/summary/retry?summaryPath=...
 
 Failure summary notes include a clickable retry link using `Api:PublicBaseUrl`, for example `http://localhost:5090/meetings/summary/retry?summaryPath=20260519-124110-summary.md`. The GET endpoint exists for Obsidian/browser clicks and performs the same overwrite behavior as the POST endpoint. Meeting note bodies stay reserved for user-authored notes.
 
-The summary agent currently has meeting-scoped tools to read the transcript, full meeting note including frontmatter, assistant context, user notes, glossary, and project files. Every read tool that returns file-like content can read the whole content or a clamped inclusive 1-based line range with `from` and `to`, so the agent can inspect large transcripts incrementally. The assistant context note is the agent's notebook and user-visible context window; the agent can write internal notes, discovered context, missing tool requests, suggested improvements, or follow-up task ideas there using line-based overwrite, replace, and insert modes. Project lookup and search tools are constrained to the projects listed in the meeting note frontmatter:
+The summary agent currently has meeting-scoped tools to read the transcript, full meeting note including frontmatter, assistant context, user notes, glossary, and project files. Every read tool that returns file-like content can read the whole content or a clamped inclusive 1-based line range with `from` and `to`, so the agent can inspect large transcripts incrementally. The assistant context note is the agent's notebook and user-visible context window; the agent can write internal notes, discovered context, missing tool requests, suggested improvements, or follow-up task ideas there using append-by-default, explicit whole-file replacement, replace, and insert modes. Project lookup and search tools are constrained to the projects listed in the meeting note frontmatter:
 
 When assistant context contains cropped screenshot links produced by OCR, the summary instructions tell the agent to include only the most relevant cropped screenshots in the summary and markdown-link them near the related summary text.
 
@@ -308,7 +308,7 @@ When assistant context contains cropped screenshot links produced by OCR, the su
 
 `search` accepts ripgrep syntax and returns matches as `filename:line text`. If one project is searched, paths are relative to that project; if multiple projects are searched, paths include the project folder name.
 
-`write_projectfile` writes inside an existing project folder. With no line arguments it overwrites or creates the file. With `from` and `to` it replaces that inclusive 1-based line range. With `insert` it inserts content at that 1-based line position.
+`write_projectfile` writes inside an existing project folder. With no line arguments it appends or creates the file. With `replace_file: true` it replaces the whole file. With `from` and `to` it replaces that inclusive 1-based line range. With `insert` it inserts content at that 1-based line position.
 
 ## Spec Workflow