fix: remove hard-coded paths from test-prerequisites, document environment assumptions

CRITICAL BUG FIX (A1):
- test-prerequisites.spec.ts used hard-coded /Users/johanneshoppe/... paths
- Tests would fail on CI and all other machines
- This invalidated "production-ready" status

Changes to test-prerequisites.spec.ts:
1. Added const projectRoot = process.cwd() for dynamic path resolution
2. Replaced all hard-coded cwd: '/Users/johanneshoppe/...' with cwd: projectRoot
3. Updated error messages to use ${projectRoot} template strings
4. Lines changed: 65, 67, 77, 85, 113, 115

Changes to TEST_COVERAGE_PLAN.md:
1. B1 - Added "Test Environment Requirements" section (lines 252-272)
   - Documents git availability requirements
   - Documents working directory assumptions (process.cwd())
   - Documents real git integration test dependencies
   - Provides CI setup guidance

2. B2 - Added "Known Upgrade Tripwires" section (lines 216-240)
   - Documents intentionally pinned gh-pages v3.2.3 behaviors
   - Lists getRemoteUrl error message assertions
   - Lists dotfiles behavior assertions
   - Lists PublishOptions mapping tests
   - Explains these are FEATURES for upgrade verification

Test results:
- test-prerequisites.spec.ts: All 3 tests pass ✅
- Full suite: All 380 tests pass ✅
- Tests now portable across all machines with proper git setup

Honest status update:
- Previous claim: "100% complete, production-ready, zero gaps"
- Reality: Critical portability bug made tests fail outside original machine
- Current: Upgrade-ready with strong v3.2.3 baseline and portable tests

Author: JohannesHoppe

TEST_COVERAGE_PLAN.md

@@ -213,6 +213,32 @@ We intentionally rely on the existing test suite for upgrade verification rather
 
 We do NOT maintain automated tooling to run tests against both versions simultaneously. This is intentional - the manual comparison process ensures careful evaluation of each change. If automated comparison becomes necessary, it can be added later.
 
+### Known Upgrade Tripwires
+
+The following tests are **INTENTIONALLY pinned** to gh-pages v3.2.3 behavior and **EXPECTED to fail** on upgrade:
+
+1. **getRemoteUrl Error Messages** (`engine.prepare-options-helpers.spec.ts`):
+   - Exact error text assertions for:
+     - "not a git repository" errors
+     - "No such remote 'xyz'" errors
+     - "remote.XYZ.url not found" errors
+   - **Action on upgrade**: Review gh-pages v6 error messages and update assertions to match new text
+   - **Why pinned**: These guard against silent API changes in gh-pages/lib/git.js
+
+2. **Dotfiles Behavior** (`engine.gh-pages-behavior.spec.ts`):
+   - File list assertions verify exact files published with `dotfiles: true/false`
+   - Tests assert specific file counts (4 files vs 3 files)
+   - **Action on upgrade**: Verify actual file lists with gh-pages v6 and update expectations
+   - **Why pinned**: Ensures dotfiles logic didn't change behavior
+
+3. **PublishOptions Mapping** (`engine.gh-pages-integration.spec.ts`):
+   - Tests verify which options are passed vs filtered
+   - Hardcoded list of options that should NOT reach gh-pages.publish
+   - **Action on upgrade**: Check if gh-pages v6 accepts new options or rejects old ones
+   - **Why pinned**: Guards against breaking changes in gh-pages API surface
+
+**These are FEATURES, not bugs** - they provide upgrade verification and ensure conscious adaptation rather than silent breakage.
+
 ---
 
 ## Implementation Order
@@ -249,6 +275,29 @@ We do NOT maintain automated tooling to run tests against both versions simultan
 
 ---
 
+## Test Environment Requirements
+
+Tests assume the following environment setup (enforced by test-prerequisites.spec.ts):
+
+1. **Git Availability**:
+   - Git executable on PATH
+   - Running in a git repository
+   - Origin remote configured
+
+2. **Working Directory**:
+   - Tests run from project root (uses `process.cwd()`)
+   - Assumes origin points to angular-schule/angular-cli-ghpages (or SSH equivalent)
+
+3. **Real Git Integration Tests**:
+   - `engine.prepare-options-helpers.spec.ts` getRemoteUrl tests depend on actual git repo
+   - See `test-prerequisites.spec.ts` for canonical environment validation
+
+**CI Setup**: Ensure CI clones the repo normally and runs tests from repo root.
+
+**Portability**: Tests use `process.cwd()` for dynamic path resolution, not hard-coded paths.
+
+---
+
 ## Files to Create/Modify
 
 **New Files:**

src/test-prerequisites.spec.ts

@@ -11,6 +11,8 @@ import { execSync } from 'child_process';
  */
 
 describe('Test Prerequisites', () => {
+  const projectRoot = process.cwd();
+
   describe('Git availability', () => {
     let gitVersion: string;
 
@@ -62,7 +64,7 @@ describe('Test Prerequisites', () => {
         gitDir = execSync('git rev-parse --git-dir', {
           encoding: 'utf8',
           stdio: 'pipe',
-          cwd: '/Users/johanneshoppe/Work/angular-schule/angular-cli-ghpages'
+          cwd: projectRoot
         }).trim();
       } catch (error) {
         throw new Error(
@@ -74,13 +76,13 @@ describe('Test Prerequisites', () => {
             'angular-cli-ghpages tests must run within a git repository.\n' +
             '\n' +
             'Current directory:\n' +
-            '  /Users/johanneshoppe/Work/angular-schule/angular-cli-ghpages\n' +
+            `  ${projectRoot}\n` +
             '\n' +
             'To fix this:\n' +
             '\n' +
             '  If you cloned this repository:\n' +
             '    # Ensure you are in the correct directory\n' +
-            '    cd /Users/johanneshoppe/Work/angular-schule/angular-cli-ghpages\n' +
+            `    cd ${projectRoot}\n` +
             '    git status\n' +
             '\n' +
             '  If you downloaded as ZIP:\n' +
@@ -110,7 +112,7 @@ describe('Test Prerequisites', () => {
         remoteUrl = execSync('git config --get remote.origin.url', {
           encoding: 'utf8',
           stdio: 'pipe',
-          cwd: '/Users/johanneshoppe/Work/angular-schule/angular-cli-ghpages'
+          cwd: projectRoot
         }).trim();
       } catch (error) {
         throw new Error(