test(perf): overhaul performance and memory baseline management

Comprehensive automation upgrades for performance and memory baselines. Includes GitHub Actions workflows for remote updates, automatic local comparisons against main, and git-ignored temporary baselines.

- Added update-baselines.yml GitHub Action to automate remote baseline upgrades efficiently in CI.
- Created scripts/run-perf-tests.js to wrap performance executions, safely stashing dirty alterations and gathering main-branch baselines locally when run without arguments.
- Enhanced PerfTestHarness and MemoryTestHarness to accommodate tolerance limits assertions safely.
- Updated test files to process TEMP_BASELINES_PATH environment variables, protecting tracked files clean during local evaluations.
- Formed docs/performance-and-memory-testing.md safely centrally detailing general strategies.
- Obsoleted folder files perf-tests/README.md, and memory-tests/README.md deleted altogether.
- Registered temporary baseline outputs inside .gitignore and updated scripts/clean.js safely for fast removals on npm run clean.

perf-tests/perf-usage.test.ts

@@ -5,13 +5,18 @@
  */
 
 import { describe, it, beforeAll, afterAll } from 'vitest';
-import { TestRig, PerfTestHarness } from '@google/gemini-cli-test-utils';
+import {
+  TestRig,
+  PerfTestHarness,
+  resolvePerfBaselinesPath,
+} from '@google/gemini-cli-test-utils';
 import { join, dirname } from 'node:path';
 import { fileURLToPath } from 'node:url';
 import { existsSync, readFileSync } from 'node:fs';
 
 const __dirname = dirname(fileURLToPath(import.meta.url));
-const BASELINES_PATH = join(__dirname, 'baselines.json');
+const MACHINE_FAMILY = process.env['PERF_MACHINE_FAMILY'];
+const BASELINES_PATH = resolvePerfBaselinesPath(__dirname, MACHINE_FAMILY);
 const UPDATE_BASELINES = process.env['UPDATE_PERF_BASELINES'] === 'true';
 const TOLERANCE_PERCENT = 15;
 
@@ -28,6 +33,7 @@ describe('CPU Performance Tests', () => {
       defaultTolerancePercent: TOLERANCE_PERCENT,
       sampleCount: SAMPLE_COUNT,
       warmupCount: WARMUP_COUNT,
+      machineFamily: MACHINE_FAMILY,
     });
   });