add(doc)[rel]: document default ignores

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

Author: ryansuhartanto

AGENTS.md

@@ -147,6 +147,10 @@ Conventions visible in the code:
   without `allowed` is flexible (anything between the delimiters).
 - Enclosure order is positional: each `[[commit.enclosures]]` entry
   may appear at most once, in declaration order.
+- Machine-generated headers — merges, reverts, `fixup!`/`squash!`/
+  `amend!`, semver release bumps — exit 0 without linting
+  (`src/ignore.rs`, mirroring commitlint's default ignores) unless
+  `default-ignores = false` is set in `[commit]`.
 - `ExtraContext::new` sorts keywords/modifiers longest-first so that
   e.g. `!!` wins over `!`. Any new token class with overlapping
   prefixes needs the same treatment.

crates/atypical-commit/README.md

@@ -42,6 +42,7 @@ keywords = ["add", "rem", "ref", "fix", "undo", "release"]
 modifiers = ["?", "!", "!!"]
 separator = ":"
 modifier-sequence = "pre" # before the enclosures, or "post"
+default-ignores = true    # skip machine-generated headers
 
 # Scopes; omit `allowed` to accept anything between the delimiters.
 [[commit.enclosures]]
@@ -57,6 +58,24 @@ allowed = [
 ]
 ```
 
+### Default ignores
+
+Headers that git and forges generate on their own are exempt from
+linting, mirroring [commitlint's default
+ignores](https://commitlint.js.org/reference/configuration.html#defaultignores):
+
+- merges: `Merge pull request ...`, `Merge branch '...'`,
+  `Merge tag '...'`, `Merge x into y`,
+  `Merge remote-tracking branch '...'`, `Merged x in(to) y`,
+  `Merged PR 1: ...`, `Automatic merge ...`, `Auto-merged x into y`
+- reverts and reapplies: `Revert "..."`, `Reapply "..."`
+- autosquash markers: `fixup! ...`, `squash! ...`, `amend! ...`
+- release bumps: a semver version, optionally behind a `chore:`
+  prefix and a `[skip ci]`-style marker, e.g. `chore(release): v1.2.3`
+
+Set `default-ignores = false` in the `[commit]` section to lint these
+like any other header.
+
 ### As a `commit-msg` hook
 
 With [husky](https://typicode.github.io/husky/), in `.husky/commit-msg`: