Email delivery test step + step-form extension point

Demonstrates the drop-in pattern: adding a step with a form is a single
new file under includes/steps/, plus one small extension to the base
abstraction.

WPH_Step gains:
- render_extra($session_state) — emit extra HTML inside the step card
- handle_action($name, $input) — handle a step-specific POST and
  return a finding to record

New generic admin-post handler wph_step_action routes form submissions
to the matching step's handle_action() with nonce verification.

The email step (includes/steps/115-email.php):
- Detects 7 known SMTP plugins, surfaces default From address
- Renders a To: input prefilled with the current admin's email
- Sends via wp_mail() with wp_mail_failed capture so failures show the
  underlying error
- Records the outcome as a 'last_send' finding so it appears on the
  step card, in the summary, and in the downloadable report

.beads/issues.jsonl

@@ -6,6 +6,7 @@
 {"_type":"issue","id":"hc-5ix.4","title":"Session data model: option-backed in-progress healthcheck record","description":"One in-progress session per site at a time. Stored in a custom option (or a CPT — pick during implementation). Shape: id, started_at, finished_at, technician_id, site_url_snapshot, per_step_state { status: not_started|in_progress|done|skipped|blocked|n_a, notes, completed_at }. Designed so phase-3 automation can attach structured findings later.","notes":"Built in phase-1 scaffold; passing lint + WP-eval end-to-end smoke test on testsite.","status":"closed","priority":1,"issue_type":"task","owner":"steve@hanlon.co.uk","created_at":"2026-06-11T14:36:11Z","created_by":"Steve Hanlon","updated_at":"2026-06-11T14:49:27Z","started_at":"2026-06-11T14:41:27Z","closed_at":"2026-06-11T14:49:27Z","labels":["phase-1"],"dependencies":[{"issue_id":"hc-5ix.4","depends_on_id":"hc-5ix","type":"parent-child","created_at":"2026-06-11T15:36:11Z","created_by":"Steve Hanlon","metadata":"{}"}],"dependency_count":0,"dependent_count":0,"comment_count":0}
 {"_type":"issue","id":"hc-5ix.2","title":"Plugin skeleton: header, activation hook, deactivation hook, admin menu (Tools → Site Healthcheck), capability gate","notes":"Built in phase-1 scaffold; passing lint + WP-eval end-to-end smoke test on testsite.","status":"closed","priority":1,"issue_type":"task","owner":"steve@hanlon.co.uk","created_at":"2026-06-11T14:36:10Z","created_by":"Steve Hanlon","updated_at":"2026-06-11T14:49:26Z","started_at":"2026-06-11T14:41:27Z","closed_at":"2026-06-11T14:49:26Z","labels":["phase-1"],"dependencies":[{"issue_id":"hc-5ix.2","depends_on_id":"hc-5ix","type":"parent-child","created_at":"2026-06-11T15:36:09Z","created_by":"Steve Hanlon","metadata":"{}"}],"dependency_count":0,"dependent_count":0,"comment_count":0}
 {"_type":"issue","id":"hc-5ix.1","title":"Bootstrap: trigger install of wp-site-recovery plugin as step 0","description":"Healthcheck plugin should check on activation if site-recovery is installed; if not, fetch and install from a known URL/ZIP and activate it. Block stepper from starting until recovery is in place.","notes":"Detection half done (status panel + manual link). Auto-install of recovery plugin from a private URL is the wp-site-recovery side of hc-5ix.27 — closing this as 'detection complete'.","status":"closed","priority":1,"issue_type":"task","owner":"steve@hanlon.co.uk","created_at":"2026-06-11T11:26:40Z","created_by":"Steve Hanlon","updated_at":"2026-06-11T15:03:02Z","closed_at":"2026-06-11T15:03:02Z","labels":["phase-1"],"dependencies":[{"issue_id":"hc-5ix.1","depends_on_id":"hc-5ix","type":"parent-child","created_at":"2026-06-11T12:26:39Z","created_by":"Steve Hanlon","metadata":"{}"}],"dependency_count":0,"dependent_count":0,"comment_count":0}
+{"_type":"issue","id":"hc-5ix.28","title":"Step — Email Delivery Test (send wp_mail to chosen address)","description":"Add a new step that sends a test email via wp_mail() to an address the technician types in. Should detect SMTP plugins in use, surface wp_mail_failed errors, and store the result as a finding so it lands in the report.\n\nDrives a small architectural extension: WPH_Step gains optional render_extra() (output HTML inside the card) and handle_action() (handle a step-specific POST), plus a generic wph_step_action admin-post handler. Demonstrates the drop-in extensibility — adding the step is a single file plus a tiny hook addition.","notes":"Added in commit (next). New file includes/steps/115-email.php — drop-in step, no other source changes beyond the small WPH_Step extension (render_extra + handle_action) and one admin-post handler (wph_step_action). Demonstrates the extensibility pattern: a step can declare its own form + handler without touching any other file.\n\nSmoke-tested on testsite: step appears in correct slot (between small_fixes and wrap_up), autocheck surfaces mailer detection (PHP mail vs. 7 known SMTP plugins) and default From address, render_extra outputs a To: input prefilled with current user's email, handle_action rejects invalid addresses and successfully sends via wp_mail (caught by Local's MailHog).","status":"closed","priority":2,"issue_type":"task","owner":"steve@hanlon.co.uk","created_at":"2026-06-11T17:43:34Z","created_by":"Steve Hanlon","updated_at":"2026-06-11T17:45:47Z","closed_at":"2026-06-11T17:45:47Z","labels":["phase-1"],"dependencies":[{"issue_id":"hc-5ix.28","depends_on_id":"hc-5ix","type":"parent-child","created_at":"2026-06-11T18:43:33Z","created_by":"Steve Hanlon","metadata":"{}"}],"dependency_count":0,"dependent_count":0,"comment_count":0}
 {"_type":"issue","id":"hc-5ix.9","title":"Smoke test on testsite: full end-to-end run through the checklist","notes":"Built in phase-1 scaffold; passing lint + WP-eval end-to-end smoke test on testsite.","status":"closed","priority":2,"issue_type":"task","owner":"steve@hanlon.co.uk","created_at":"2026-06-11T14:36:15Z","created_by":"Steve Hanlon","updated_at":"2026-06-11T14:49:29Z","closed_at":"2026-06-11T14:49:29Z","labels":["phase-1"],"dependencies":[{"issue_id":"hc-5ix.9","depends_on_id":"hc-5ix","type":"parent-child","created_at":"2026-06-11T15:36:14Z","created_by":"Steve Hanlon","metadata":"{}"}],"dependency_count":0,"dependent_count":0,"comment_count":0}
 {"_type":"issue","id":"hc-5ix.8","title":"README + install instructions + screenshots placeholder","notes":"Built in phase-1 scaffold; passing lint + WP-eval end-to-end smoke test on testsite.","status":"closed","priority":2,"issue_type":"chore","owner":"steve@hanlon.co.uk","created_at":"2026-06-11T14:36:14Z","created_by":"Steve Hanlon","updated_at":"2026-06-11T14:49:29Z","closed_at":"2026-06-11T14:49:29Z","labels":["phase-1"],"dependencies":[{"issue_id":"hc-5ix.8","depends_on_id":"hc-5ix","type":"parent-child","created_at":"2026-06-11T15:36:14Z","created_by":"Steve Hanlon","metadata":"{}"}],"dependency_count":0,"dependent_count":0,"comment_count":0}
 {"_type":"issue","id":"hc-5ix","title":"Build WordPress Healthcheck plugin (stepper through steps.md)","description":"Plugin that walks a technician through the WordPress healthcheck steps documented in steps.md. Independent of the recovery plugin (which it depends on as step 0).","status":"open","priority":2,"issue_type":"epic","owner":"steve@hanlon.co.uk","created_at":"2026-06-11T11:26:32Z","created_by":"Steve Hanlon","updated_at":"2026-06-11T11:26:32Z","dependency_count":0,"dependent_count":0,"comment_count":0}