Show workspace commits clearly in Changes (#2350)

* feat(commits): distinguish workspace history from base commits

Keep every workspace commit visible while bounding base history to ten
context commits, and make push and base state readable in the commit rail.

* fix(commits): preserve history when base refs disappear

Fall back to recent HEAD history for stale saved bases, and reject truncated
git output instead of presenting an incomplete commit list.

* fix(commits): classify history against the current base

Use the furthest-ahead local or remote base for classification, and re-infer
base history when saved worktree metadata points to a deleted branch.

packages/protocol/src/messages.ts

@@ -1732,6 +1732,8 @@ const CheckoutCommitSchema = z.object({
   authorName: z.string(),
   authorDate: z.string(), // ISO 8601
   isOnRemote: z.boolean(), // false = local-only (unpushed)
+  // COMPAT(commitBaseClassification): added in v0.2.0, remove optional after 2027-01-23.
+  isOnBase: z.boolean().optional(),
   files: z.array(CheckoutCommitFileSchema),
 });
 
@@ -2777,6 +2779,8 @@ export const ServerInfoStatusPayloadSchema = z
         projectCreateDirectory: z.boolean().optional(),
         // COMPAT(commitsList): added in v0.1.110, remove gate after 2027-01-16.
         commitsList: z.boolean().optional(),
+        // COMPAT(commitBaseClassification): added in v0.2.0, remove gate after 2027-01-23.
+        commitBaseClassification: z.boolean().optional(),
         // COMPAT(providerRemoval): added in v0.1.105, drop the gate when floor >= v0.1.105.
         providerRemoval: z.boolean().optional(),
         // COMPAT(importSessionWorkspaceTarget): added in v0.1.110, remove gate after 2027-01-16.