Docs: GETTING-STARTED optional 007-ThrowsWeb presenter step (curl invalid POST)

[PurHur]

Problem

docs/GETTING-STARTED.md documents 005-SessionsWeb (§5) and 006-FileUploadWeb (§5a) presenter flows. 007-ThrowsWeb has README + make examples-throws-smoke (#2141) but no five-minute demo section for new contributors.

Goal

Add an optional subsection (e.g. §5b) with copy-paste:

./phpc serve 127.0.0.1:8080 examples/007-ThrowsWeb
curl -sf -X POST -d 'email=bad' http://127.0.0.1:8080/example.php | grep -i invalid
make examples-throws-smoke   # when #2141 lands

Note AOT deferred until #2157 (link to issue).

Scope

File	Change
docs/GETTING-STARTED.md	New §5b + TOC entry
README.md	Optional one-line pointer under Demo table
test/unit/GettingStartedDocTest.php	If exists, assert 007-ThrowsWeb needle

Acceptance criteria

• Section renders on status site pipeline (if linked from docs/README.md)
• Commands verified on harness with phpc serve bind available

Dependencies

• Examples: 007-ThrowsWeb — throw/catch presenter app (post-#195/#57) #2076 ✅ — example tree
• Testing: make examples-throws-smoke target (007-ThrowsWeb) #2141 — make examples-throws-smoke (docs can reference script path before target lands)
• Language: AOT throw/catch with user-defined class (007 ValidationError execute) #2157 — note AOT path when green

Verification

Doc-only — no GHA; spot-check locally.

Links

• Pattern: Docs: GETTING-STARTED optional step — 005-SessionsWeb session flash demo #1958 (005), Docs: GETTING-STARTED optional step — 006-FileUploadWeb multipart upload demo #2043 (006)
• ROADMAP 🗺️ ROADMAP: Self-host + web-capable PHP subset (living) #78 Phase 4 Polish