fix(server): accept Git-valid worktree branch names (#3591)

Branch-off creation reused the filesystem slug validator even when callers supplied a separate branch name and worktree slug. Validate branch refs with Git at the worktree boundary so exact valid refs are preserved while path slugs remain restricted.

packages/server/src/utils/worktree.ts

@@ -42,7 +42,6 @@ import { spawnProcess } from "./spawn.js";
 import { resolvePaseoHome } from "../server/paseo-home.js";
 import { createExternalProcessEnv } from "../server/paseo-env.js";
 import { parseGitRevParsePath, resolveGitRevParsePath } from "./git-rev-parse-path.js";
-import { validateBranchSlug } from "@getpaseo/protocol/branch-slug";
 import { expandTilde, getRealpathAwareRelativePath, isPathInsideRoot } from "./path.js";
 import { terminateWithTreeKill } from "./tree-kill.js";
 
@@ -1310,7 +1309,7 @@ async function resolveWorktreeSourcePlan({
   switch (source.kind) {
     case "branch-off": {
       const branchName = source.branchName;
-      validateWorktreeBranchName(branchName);
+      await validateGitBranchName(cwd, branchName);
       const normalizedBaseBranch = normalizeRequiredBaseBranch(source.baseBranch);
       const resolvedBaseBranch = await resolveBaseBranchForWorktree(cwd, source.baseBranch);
       const branchExists = await localBranchExists(cwd, branchName);
@@ -1330,7 +1329,7 @@ async function resolveWorktreeSourcePlan({
       };
     }
     case "checkout-branch": {
-      await validateExistingWorktreeBranchName(cwd, source.branchName);
+      await validateGitBranchName(cwd, source.branchName);
       if (!(await localBranchExists(cwd, source.branchName))) {
         try {
           await runGitCommand(["fetch", "origin", `${source.branchName}:${source.branchName}`], {
@@ -1367,7 +1366,7 @@ async function resolveWorktreeSourcePlan({
     case "checkout-change-request":
     case "checkout-github-pr": {
       const localBranchCandidate = source.localBranchName ?? source.headRef;
-      await validateExistingWorktreeBranchName(cwd, localBranchCandidate);
+      await validateGitBranchName(cwd, localBranchCandidate);
       const localBranchName = await resolveUniqueLocalBranchName(cwd, localBranchCandidate);
       const normalizedBaseRefName = normalizeRequiredBaseBranch(source.baseRefName);
       const changeRequestNumber =
@@ -1589,14 +1588,7 @@ async function configureWorktreeTrackingRemote(options: {
   );
 }
 
-function validateWorktreeBranchName(branchName: string): void {
-  const validation = validateBranchSlug(branchName);
-  if (!validation.valid) {
-    throw new Error(`Invalid branch name: ${validation.error}`);
-  }
-}
-
-async function validateExistingWorktreeBranchName(cwd: string, branchName: string): Promise<void> {
+async function validateGitBranchName(cwd: string, branchName: string): Promise<void> {
   const result = await runGitCommand(["check-ref-format", "--branch", branchName], {
     cwd,
     timeout: 30_000,