chore: update CI Go matrix to latest two releases (1.24, 1.25)

Updates all GitHub Actions workflows to use Go 1.24 and 1.25,
dropping support for older versions (1.21, 1.22, 1.23).

Changes:
- ci.yml: Update test matrix to ['1.24', '1.25']
- ci.yml: Update all hardcoded versions to 1.25 (build, lint, cross-compile, e2e-macos)
- ci.yml: Update codecov condition to use 1.25
- e2e-linux.yml: Update to Go 1.25
- release.yml: Update build jobs to Go 1.25

Resolves beads-oss-tasks-9v7

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>

Author: timvw

.github/workflows/ci.yml

@@ -13,7 +13,7 @@ jobs:
     runs-on: ubuntu-latest
     strategy:
       matrix:
-        go-version: ['1.21', '1.22', '1.23']
+        go-version: ['1.24', '1.25']
 
     steps:
       - name: Generate GitHub App token
@@ -43,7 +43,7 @@ jobs:
         run: go test -v -race -coverprofile=coverage.out ./...
 
       - name: Upload coverage to Codecov
-        if: matrix.go-version == '1.23'
+        if: matrix.go-version == '1.25'
         uses: codecov/codecov-action@v5
         with:
           token: ${{ secrets.CODECOV_TOKEN }}
@@ -71,7 +71,7 @@ jobs:
       - name: Set up Go
         uses: actions/setup-go@v5
         with:
-          go-version: '1.23'
+          go-version: '1.25'
 
       - name: Build
         run: go build -v ./...
@@ -106,7 +106,7 @@ jobs:
       - name: Set up Go
         uses: actions/setup-go@v5
         with:
-          go-version: '1.23'
+          go-version: '1.25'
 
       - name: Run golangci-lint
         uses: golangci/golangci-lint-action@v4
@@ -133,7 +133,7 @@ jobs:
       - name: Set up Go
         uses: actions/setup-go@v5
         with:
-          go-version: '1.23'
+          go-version: '1.25'
 
       - name: Cross compile
         run: |
@@ -171,7 +171,7 @@ jobs:
       - name: Set up Go
         uses: actions/setup-go@v5
         with:
-          go-version: '1.23'
+          go-version: '1.25'
 
       - name: Download dependencies
         run: go mod download

.github/workflows/e2e-linux.yml

@@ -34,7 +34,7 @@ jobs:
       - name: Set up Go
         uses: actions/setup-go@v5
         with:
-          go-version: '1.23'
+          go-version: '1.25'
 
       - name: Install zsh
         if: matrix.shell == 'zsh'

.github/workflows/release.yml

@@ -48,7 +48,7 @@ jobs:
       - name: Set up Go
         uses: actions/setup-go@v5
         with:
-          go-version: '1.23'
+          go-version: '1.25'
 
       - name: Extract version from tag
         id: version
@@ -108,7 +108,7 @@ jobs:
       - name: Set up Go
         uses: actions/setup-go@v5
         with:
-          go-version: '1.23'
+          go-version: '1.25'
 
       - name: Build Windows binary
         env: