feat(matching): add an opt-in regex keyword matching mode

Fuzzy matching compares each keyword with every word of the commit
message. A word matches if it contains the keyword's letters in order.
Thus "feat" matches "fix(delegation):" and "major" matches
"deps(majors):", which gives false minor and major versions.

The new top-level config key "matching" accepts "fuzzy" (the default)
or "regex". In regex mode every wording keyword is a Go regular
expression. The tool compiles all of them when it loads the config and
runs them against the full commit message, so "(?m)^" anchors a
pattern to the start of a line. An invalid value, an invalid pattern,
or any other config parse error in regex mode stops the tool with a
non-zero exit code. It never falls back to fuzzy matching.

Fuzzy mode does not change. The blacklist check moves into one helper
that both modes use. A replay of 15 repositories gives the same
versions as before. This change improves version precision for the
repositories that opt in.

Claude-Session: https://claude.ai/code/session_01Qq1gbqQek1Zjtofo4VDRdW

cmd/utils/semver.go

@@ -9,12 +9,19 @@ func CalculateSemver(
 	commits []CommitDetails,
 	tags []TagDetails,
 	wording Wording,
+	matcher KeywordMatcher,
 	blacklist []string,
 	initialSemver SemVer,
 	respectExisting bool,
 	strictMode bool,
 	tagPrefixes []string,
 ) SemVer {
+	// Default-preserving: callers that don't select a matcher get today's
+	// fuzzy behaviour rather than a nil-pointer panic.
+	if matcher == nil {
+		matcher = FuzzyMatcher{}
+	}
+
 	semver := initialSemver
 	startIndex := 0
 
@@ -57,11 +64,10 @@ func CalculateSemver(
 		}
 
 		// Check for keyword matches
-		commitSlice := strings.Fields(commit.Message)
-		matchPatch := CheckMatches(commitSlice, wording.Patch, blacklist)
-		matchMinor := CheckMatches(commitSlice, wording.Minor, blacklist)
-		matchMajor := CheckMatches(commitSlice, wording.Major, blacklist)
-		matchReleaseCandidate := CheckMatches(commitSlice, wording.Release, blacklist)
+		matchPatch := matcher.Matches(commit.Message, wording.Patch, blacklist)
+		matchMinor := matcher.Matches(commit.Message, wording.Minor, blacklist)
+		matchMajor := matcher.Matches(commit.Message, wording.Major, blacklist)
+		matchReleaseCandidate := matcher.Matches(commit.Message, wording.Release, blacklist)
 
 		// Apply version changes based on matches
 		if matchMajor {