docs: add documentation for 5 low-priority undocumented SHAFT_ENGINE features

[Copilot]

Five SHAFT_ENGINE APIs identified in the documentation gap analysis (issue #440) had no coverage on the docs site. This PR adds dedicated pages for all 🟢 low-priority items.

New pages

• docs/Reporting/Custom_Report_Messages.md — withCustomReportMessage() on validation chains + the SHAFT.Report programmatic API (log(), report(), attach())
• docs/Keywords/CLI/Docker_Terminal.md — TerminalActions Docker constructor for executing commands inside running containers
• docs/Keywords/CLI/SSH_Terminal.md — TerminalActions SSH constructor with key-based auth and FileActions remote file transfer
• docs/Keywords/GUI/didYouKnow/Clipboard_Actions.md — driver.element().clipboardActions() with the ClipboardAction enum (COPY, CUT, PASTE, SELECT_ALL)
• docs/Keywords/GUI/didYouKnow/Kubernetes_Selenium_Grid.md — Deploying Selenium Grid on Kubernetes with KEDA auto-scaling via Helm and pointing SHAFT at the cluster-internal service DNS

Sidebar changes

• CLI category: Docker Terminal and SSH Terminal inserted after Terminal Actions
• GUI › Did You Know category: Kubernetes Grid and Clipboard Actions appended
• Reporting: promoted from a single doc link to a collapsible category containing the existing Reporting page + the new Custom Report Messages page

Representative snippet

// Custom validation message — appears verbatim in the Allure step name
driver.assertThat()
    .browser().url().contains("/dashboard")
    .withCustomReportMessage("URL must contain /dashboard after successful login")
    .perform();

// Clipboard cut-and-paste chain
driver.element()
    .clipboardActions(By.id("editField"), ClipboardAction.SELECT_ALL)
    .clipboardActions(By.id("editField"), ClipboardAction.CUT)
    .clipboardActions(By.id("newField"),  ClipboardAction.PASTE);

// K8s Grid — point SHAFT at the in-cluster service
SHAFT.Properties.platform.set()
    .executionAddress("selenium-grid-selenium-hub.default.svc.cluster.local:4444");

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