Match .gitignore, .editorconfig and .golangci.yml to sneak/prompts (closes #174)

REPO_POLICIES.md asks for the standard .gitignore and .editorconfig
followed by the repository's own entries, and for the canonical
.golangci.yml. The shared parts and .golangci.yml now match the
sneak/prompts copies at 065357920a0a09bd736bf33d4cb5ce935fdc2328 byte
for byte. .editorconfig has no entries of its own left, since the
standard file now carries the [*.go] section. .golangci.yml disables
canonicalheader, as the canonical copy does.

Model: opus-5-5

TODO.md

@@ -22,6 +22,13 @@ Run `make frontend-viewport-test` in CI as its own step; it is not part of
 
 # Completed Steps
 
+- 2026-10-19: `.gitignore`, `.editorconfig` and `.golangci.yml` are the
+  sneak/prompts copies at `0653579`
+  ([#174](https://git.eeqj.de/sneak/netwatch/issues/174)). `.gitignore` is the
+  standard file followed by this repository's own entries; `.editorconfig` is
+  the standard file alone, which now carries the `[*.go]` section.
+  `.golangci.yml` disables `canonicalheader`, as the canonical copy does,
+  because golangci-lint v2.14.0 misses its findings at random
 - 2026-10-19: `netwatch-server` starts the server only when given no arguments
   ([#179](https://git.eeqj.de/sneak/netwatch/issues/179)). `check-cidr CIDR` and
   `prepare-data-dir DATA_DIR` behave as before; any other arguments, such as a