[Registrar] Add 5 new docs pages from April 2026 support case gap analysis

[travisgahn]

Summary

Adds 5 new documentation pages to the Registrar section based on a gap analysis of ~350 April 2026 support cases. These pages address the top documentation gaps driving 46% of total Registrar ticket volume.

Tracked in SPM-3500.

New pages

Page	Path	Priority	Est. deflection
Refunds and cancellations	/registrar/account-options/refunds-and-cancellations/	P0	~55 cases/mo (16%)
Email verification	/registrar/account-options/email-verification/	P0	~45 cases/mo (13%)
Registration errors	/registrar/registration-errors/	P0	~60 cases/mo (17%)
Nameserver changes	/registrar/nameserver-changes/	P1	~30 cases/mo (9%)
.ca domains	/registrar/top-level-domains/ca-domains/	P1	~12 cases/mo (3%)

Context

The top 3 Registrar support case categories in April 2026 had zero documentation coverage:

1. Refund/cancellation requests (16%) — customers do not know the refund policy, ICANN Add Grace Period, or that registrations are non-refundable
2. ICANN email verification / domain suspension (13%) — customers do not recognize emails from @emailverification.info, miss them, or have typos preventing verification
3. Registration blocked / payment failures (17%) — "temporarily blocked" errors with no troubleshooting guidance

Two additional P1 gaps:

• Nameserver drift (9%) — domains silently moved to emailverification.info nameservers with no explanation in docs
• No .ca domain guide (3%) — .ca has CIRA-specific verification requirements not covered anywhere

Style compliance

• Follows MDX frontmatter conventions (pcx_content_type, products, sidebar.order)
• Uses DashButton component for dashboard links
• Uses :::note and :::caution admonitions (Starlight syntax)
• No contractions, active voice, "select" not "click", "go to" not "navigate"
• Internal links use relative paths without file extensions
• Code blocks specify lowercase language identifiers

What is NOT in this PR (follow-up)

Modifications to existing pages (troubleshooting, FAQ, renew-domains, inter-account-transfer, whois-redaction, domain-management) are planned as a follow-up PR to keep this review focused on net-new content.