site: cut the template's own labels out of the pages

Point 7 of the page-wording review. The pages no longer show their data
structure as headings, and they no longer explain their own conventions.

- Level 1 is one screen: claim, status badge, three figures, the technology
  row, and one sentence carrying one link. Measured in headless Chrome at
  1440x900: 1404-1845 px tall before, exactly 900 px (no scroll) after, on
  all six area pages.
- DocPage: no kicker line, no visible level label, no "Evidence for this
  page" heading or instruction note, no "Drill-downs" list, no
  "Status <word> - sentence" footer. The artefact table starts at level 2,
  under the heading "Artefacts"; the history timeline is level 2 only.
- Landing page: "Start here" link text gone, "How to read this site" panel
  gone, the footer's status-label explainer gone.
- Content, presentation only, no claim softened: the leading H1 that
  duplicated the page title removed from all 41 documents; level 1 bodies
  reduced to the constraint as ordinary prose plus the way in;
  "**Status: ...**" prefixes removed from the artefact stubs; "## Drill-downs"
  and "## Period and confidence" removed from the level 2 pages, with the
  cross-area links moved into the prose.
- The six level 1 claims are now sentences with a subject, and use commas
  instead of middots. Same facts, no new ones.

Not in this commit: the 35 level 2 and 3 claims still use the compact CV
style. That is a voice decision for Sam, not a wording tidy-up.

make validate: 41 documents, 0 violations. go test ./...: pass.

(cherry picked from commit 03009f80fc7815ad7719412e125df9297a6e653f)

content/platform/l3/platform-backups.md

@@ -14,9 +14,7 @@ last_verified: 2026-10-26
 tags: [platform, backups, restore, artefact]
 ---
 
-# Artefact — Backups and restore runbook
-
-**Status: stub.** Redacted job definitions and the restore runbook land in Phase 7. Passphrase locations and remote paths are removed before publication.
+Redacted job definitions and the restore runbook land in Phase 7. Passphrase locations and remote paths are removed before publication.
 
 ## What the artefact is
 

content/platform/l3/platform-containers.md

@@ -14,9 +14,7 @@ last_verified: 2026-10-26
 tags: [platform, docker, artefact]
 ---
 
-# Artefact — Container inventory
-
-**Status: stub.** A digest of the inventory — grouped by purpose, with addresses removed — lands in Phase 7.
+A digest of the inventory — grouped by purpose, with addresses removed — lands in Phase 7.
 
 ## What the artefact is
 

content/platform/l3/platform-network.md

@@ -14,9 +14,7 @@ last_verified: 2026-10-26
 tags: [platform, networking, security, artefact]
 ---
 
-# Artefact — Network layout and remote access
-
-**Status: stub.** The topology diagram lands in Phase 7 with addresses and hostnames redacted.
+The topology diagram lands in Phase 7 with addresses and hostnames redacted.
 
 ## What the artefact is
 

content/platform/l3/platform-nixos.md

@@ -14,9 +14,7 @@ last_verified: 2026-10-26
 tags: [platform, nixos, artefact]
 ---
 
-# Artefact — Declarative multi-host configuration
-
-**Status: stub.** A redacted excerpt of the configuration tree lands in Phase 7. No hostnames, addresses or keys are published.
+A redacted excerpt of the configuration tree lands in Phase 7. No hostnames, addresses or keys are published.
 
 ## What the artefact is
 

content/platform/l3/platform-signage.md

@@ -14,9 +14,7 @@ last_verified: 2026-10-26
 tags: [platform, signage, hdmi-cec, artefact]
 ---
 
-# Artefact — Signage infrastructure · screens as a managed fleet
-
-**Status: stub.** The CEC command set and a layout diagram land in Phase 7.
+The CEC command set and a layout diagram land in Phase 7.
 
 ## What the artefact is
 

content/platform/l3/platform-tuios-package.md

@@ -14,9 +14,7 @@ last_verified: 2026-10-26
 tags: [platform, nix, packaging, artefact]
 ---
 
-# Artefact — A hand-written Nix package with an exit plan
-
-**Status: stub.** The whole file is short enough to publish verbatim; it lands in Phase 7.
+The whole file is short enough to publish verbatim; it lands in Phase 7.
 
 ## What the artefact is