fix: support feature branch numbers with 4+ digits (#2040)

* fix: support feature branch numbers with 4+ digits in common.sh and common.ps1

The sequential feature number pattern was hardcoded to exactly 3 digits
(`{3}`), causing branches like `1234-feature-name` to be rejected.
Changed to `{3,}` (3 or more digits) to support growing projects.
Also added a guard to exclude malformed timestamp patterns from being
accepted as sequential prefixes.

Closes #344

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

* fix: narrow timestamp guard and use [long] to prevent overflow

- Change [int] to [long] in PowerShell Get-CurrentBranch to avoid
  overflow for large feature numbers (>2,147,483,647)
- Narrow malformed-timestamp exclusion from ^[0-9]+-[0-9]{6}- to
  ^[0-9]{7}-[0-9]{6}- so valid sequential branches like
  004-123456-fix-bug are not rejected

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

* test: add regression tests for 4+ digit feature branch support

Cover check_feature_branch and find_feature_dir_by_prefix with 4-digit
sequential prefixes, as requested in PR review #2040.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

* fix: reject timestamp-like branches without trailing slug

Branches like "20260319-143022" (no "-<name>" suffix) were incorrectly
accepted as sequential prefixes. Add explicit rejection for 7-or-8
digit date + 6-digit time patterns with no trailing slug, in both
common.sh and common.ps1.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

---------

Co-authored-by: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

scripts/bash/common.sh

@@ -78,7 +78,7 @@ get_current_branch() {
                         latest_timestamp="$ts"
                         latest_feature=$dirname
                     fi
-                elif [[ "$dirname" =~ ^([0-9]{3})- ]]; then
+                elif [[ "$dirname" =~ ^([0-9]{3,})- ]]; then
                     local number=${BASH_REMATCH[1]}
                     number=$((10#$number))
                     if [[ "$number" -gt "$highest" ]]; then
@@ -124,9 +124,15 @@ check_feature_branch() {
         return 0
     fi
 
-    if [[ ! "$branch" =~ ^[0-9]{3}- ]] && [[ ! "$branch" =~ ^[0-9]{8}-[0-9]{6}- ]]; then
+    # Accept sequential prefix (3+ digits) but exclude malformed timestamps
+    # Malformed: 7-or-8 digit date + 6-digit time with no trailing slug (e.g. "2026031-143022" or "20260319-143022")
+    local is_sequential=false
+    if [[ "$branch" =~ ^[0-9]{3,}- ]] && [[ ! "$branch" =~ ^[0-9]{7}-[0-9]{6}- ]] && [[ ! "$branch" =~ ^[0-9]{7,8}-[0-9]{6}$ ]]; then
+        is_sequential=true
+    fi
+    if [[ "$is_sequential" != "true" ]] && [[ ! "$branch" =~ ^[0-9]{8}-[0-9]{6}- ]]; then
         echo "ERROR: Not on a feature branch. Current branch: $branch" >&2
-        echo "Feature branches should be named like: 001-feature-name or 20260319-143022-feature-name" >&2
+        echo "Feature branches should be named like: 001-feature-name, 1234-feature-name, or 20260319-143022-feature-name" >&2
         return 1
     fi
 
@@ -146,7 +152,7 @@ find_feature_dir_by_prefix() {
     local prefix=""
     if [[ "$branch_name" =~ ^([0-9]{8}-[0-9]{6})- ]]; then
         prefix="${BASH_REMATCH[1]}"
-    elif [[ "$branch_name" =~ ^([0-9]{3})- ]]; then
+    elif [[ "$branch_name" =~ ^([0-9]{3,})- ]]; then
         prefix="${BASH_REMATCH[1]}"
     else
         # If branch doesn't have a recognized prefix, fall back to exact match

scripts/powershell/common.ps1

@@ -83,8 +83,8 @@ function Get-CurrentBranch {
                     $latestTimestamp = $ts
                     $latestFeature = $_.Name
                 }
-            } elseif ($_.Name -match '^(\d{3})-') {
-                $num = [int]$matches[1]
+            } elseif ($_.Name -match '^(\d{3,})-') {
+                $num = [long]$matches[1]
                 if ($num -gt $highest) {
                     $highest = $num
                     # Only update if no timestamp branch found yet
@@ -139,9 +139,13 @@ function Test-FeatureBranch {
         return $true
     }
     
-    if ($Branch -notmatch '^[0-9]{3}-' -and $Branch -notmatch '^\d{8}-\d{6}-') {
+    # Accept sequential prefix (3+ digits) but exclude malformed timestamps
+    # Malformed: 7-or-8 digit date + 6-digit time with no trailing slug (e.g. "2026031-143022" or "20260319-143022")
+    $hasMalformedTimestamp = ($Branch -match '^[0-9]{7}-[0-9]{6}-') -or ($Branch -match '^(?:\d{7}|\d{8})-\d{6}$')
+    $isSequential = ($Branch -match '^[0-9]{3,}-') -and (-not $hasMalformedTimestamp)
+    if (-not $isSequential -and $Branch -notmatch '^\d{8}-\d{6}-') {
         Write-Output "ERROR: Not on a feature branch. Current branch: $Branch"
-        Write-Output "Feature branches should be named like: 001-feature-name or 20260319-143022-feature-name"
+        Write-Output "Feature branches should be named like: 001-feature-name, 1234-feature-name, or 20260319-143022-feature-name"
         return $false
     }
     return $true

tests/test_timestamp_branches.py

@@ -186,11 +186,26 @@ class TestCheckFeatureBranch:
         result = source_and_call('check_feature_branch "main" "true"')
         assert result.returncode != 0
 
+    def test_accepts_four_digit_sequential_branch(self):
+        """check_feature_branch accepts 4+ digit sequential branch."""
+        result = source_and_call('check_feature_branch "1234-feat" "true"')
+        assert result.returncode == 0
+
     def test_rejects_partial_timestamp(self):
         """Test 9: check_feature_branch rejects 7-digit date."""
         result = source_and_call('check_feature_branch "2026031-143022-feat" "true"')
         assert result.returncode != 0
 
+    def test_rejects_timestamp_without_slug(self):
+        """check_feature_branch rejects timestamp-like branch missing trailing slug."""
+        result = source_and_call('check_feature_branch "20260319-143022" "true"')
+        assert result.returncode != 0
+
+    def test_rejects_7digit_timestamp_without_slug(self):
+        """check_feature_branch rejects 7-digit date + 6-digit time without slug."""
+        result = source_and_call('check_feature_branch "2026031-143022" "true"')
+        assert result.returncode != 0
+
 
 # ── find_feature_dir_by_prefix Tests ─────────────────────────────────────────
 
@@ -214,6 +229,15 @@ class TestFindFeatureDirByPrefix:
         assert result.returncode == 0
         assert result.stdout.strip() == f"{tmp_path}/specs/20260319-143022-original-feat"
 
+    def test_four_digit_sequential_prefix(self, tmp_path: Path):
+        """find_feature_dir_by_prefix resolves 4+ digit sequential prefix."""
+        (tmp_path / "specs" / "1000-original-feat").mkdir(parents=True)
+        result = source_and_call(
+            f'find_feature_dir_by_prefix "{tmp_path}" "1000-different-name"'
+        )
+        assert result.returncode == 0
+        assert result.stdout.strip() == f"{tmp_path}/specs/1000-original-feat"
+
 
 # ── get_current_branch Tests ─────────────────────────────────────────────────