Initial QSfera import

Server/vendor/github.com/clipperhouse/displaywidth/AGENTS.md

@@ -0,0 +1,39 @@
+The goals and overview of this package can be found in the README.md file,
+start by reading that.
+
+The goal of this package is to determine the display (column) width of a
+string, UTF-8 bytes, or runes, as would happen in a monospace font, especially
+in a terminal.
+
+When troubleshooting, write Go unit tests instead of executing debug scripts.
+The tests can return whatever logs or output you need. If those tests are
+only for temporary troubleshooting, clean up the tests after the debugging is
+done.
+
+(Separate executable debugging scripts are messy, tend to have conflicting
+dependencies and are hard to cleanup.)
+
+If you make changes to the trie generation in internal/gen, it can be invoked
+by running `go generate` from the top package directory.
+
+## Pull Requests and branches
+
+For PRs (pull requests), you can use the gh CLI tool. Compare the current branch with main. Reviewing a PR and reviewing a branch are about the same, but the PR may add context.
+
+Understand the goals of the PR. Note any API changes, especially breaking changes.
+
+Look for thoroughness of tests, as well as GoDoc comments.
+
+Retrieve and consider the comments on the PR, which may have come from GitHub Copilot or Cursor BugBot. Think like GitHub Copilot or Cursor BugBot.
+
+Offer to optionally post a brief summary of the review to the PR, via the gh CLI tool.
+
+## Comparisons to go-runewidth
+
+We originally attempted to make this package compatible with go-runewidth.
+However, we found that there were too many differences in the handling of
+certain characters and properties.
+
+We believe, preliminarily, that our choices are more correct and complete,
+by using more complete categories such as Unicode Cf (format) for zero-width
+and Mn (Nonspacing_Mark) for combining marks.