feat(gmail): add --body-format flag to messages search

Supports "text" (default, existing behavior) and "html" to prefer
the HTML MIME part over plaintext. Useful for newsletter ingestion
where the HTML body contains the rich formatted content.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
(cherry picked from commit cb5499ed7b4d20a863de1aef07c58c94ecd9a9fe)

.byline/commits/4a477a05f.json

@@ -0,0 +1,44 @@
+{
+  "sha": "4a477a05f2f16b649211e2c77ad9e1c8c7f6e777",
+  "shortSha": "4a477a05f",
+  "parentSha": "0d0d95a00c41d5f05ecadf22f44788bd5163b2fc",
+  "timestamp": "2026-04-21T21:42:31-04:00",
+  "message": "Add byline commit classification cache files",
+  "files": {
+    ".byline/commits/0d0d95a00.json": {
+      "path": ".byline/commits/0d0d95a00.json",
+      "summary": {
+        "mine": 2214,
+        "machine": 0,
+        "ours": 0
+      },
+      "segments": []
+    },
+    ".byline/commits/c9f2e83f2.json": {
+      "path": ".byline/commits/c9f2e83f2.json",
+      "summary": {
+        "mine": 1379,
+        "machine": 0,
+        "ours": 0
+      },
+      "segments": []
+    }
+  },
+  "totals": {
+    "mine": 3593,
+    "machine": 0,
+    "ours": 0,
+    "percent": {
+      "mine": 100,
+      "machine": 0,
+      "ours": 0
+    }
+  },
+  "sessions": [],
+  "meta": {
+    "analyzedAt": "2026-04-22T01:42:31.526Z",
+    "version": "0.2.0",
+    "retroactive": false,
+    "confidence": 1
+  }
+}

internal/cmd/gmail_messages.go

@@ -28,6 +28,7 @@ type GmailMessagesSearchCmd struct {
 	Timezone    string   `name:"timezone" short:"z" help:"Output timezone (IANA name, e.g. America/New_York, UTC). Default: local"`
 	Local       bool     `name:"local" help:"Use local timezone (default behavior, useful to override --timezone)"`
 	IncludeBody bool     `name:"include-body" help:"Include decoded message body (JSON is full; text output is truncated)"`
+	BodyFormat  string   `name:"body-format" help:"Body format preference: text (default) or html" default:"text" enum:"text,html"`
 	Full        bool     `name:"full" help:"Show full message bodies without truncation (implies --include-body)"`
 }
 
@@ -88,7 +89,7 @@ func (c *GmailMessagesSearchCmd) Run(ctx context.Context, flags *RootFlags) erro
 		return err
 	}
 
-	items, err := fetchMessageDetails(ctx, svc, messages, idToName, loc, c.IncludeBody)
+	items, err := fetchMessageDetails(ctx, svc, messages, idToName, loc, c.IncludeBody, c.BodyFormat)
 	if err != nil {
 		return err
 	}
@@ -200,7 +201,8 @@ type messageItem struct {
 	Body     string   `json:"body,omitempty"`
 }
 
-func fetchMessageDetails(ctx context.Context, svc *gmail.Service, messages []*gmail.Message, idToName map[string]string, loc *time.Location, includeBody bool) ([]messageItem, error) {
+func fetchMessageDetails(ctx context.Context, svc *gmail.Service, messages []*gmail.Message, idToName map[string]string, loc *time.Location, includeBody bool, bodyFormat ...string) ([]messageItem, error) {
+	preferHTML := len(bodyFormat) > 0 && bodyFormat[0] == "html"
 	if len(messages) == 0 {
 		return nil, nil
 	}
@@ -257,7 +259,11 @@ func fetchMessageDetails(ctx context.Context, svc *gmail.Service, messages []*gm
 			item.Subject = sanitizeTab(headerValue(msg.Payload, "Subject"))
 			item.Date = formatGmailDateInLocation(headerValue(msg.Payload, "Date"), loc)
 			if includeBody {
-				item.Body = bestBodyText(msg.Payload)
+				if preferHTML {
+					item.Body = bestBodyHTML(msg.Payload)
+				} else {
+					item.Body = bestBodyText(msg.Payload)
+				}
 			}
 
 			if len(msg.LabelIds) > 0 {

internal/cmd/gmail_thread.go

@@ -377,6 +377,18 @@ func bestBodyText(p *gmail.MessagePart) string {
 	return html
 }
 
+func bestBodyHTML(p *gmail.MessagePart) string {
+	if p == nil {
+		return ""
+	}
+	html := findPartBody(p, "text/html")
+	if html != "" {
+		return html
+	}
+	plain := findPartBody(p, "text/plain")
+	return plain
+}
+
 func bestBodyForDisplay(p *gmail.MessagePart) (string, bool) {
 	if p == nil {
 		return "", false