fix(control-plane): reset knowledge state on bank switch

[pstanton237]

Background

The knowledge-base view kept page and mental-model state from the previous bank during a bank switch. Effects could then request those stale IDs against the newly selected bank, producing 404 notifications. A ?page= link containing a missing, folder, or foreign-bank ID also prevented automatic selection and left the content pane empty.

Changes

• Remount the knowledge-base view when the selected bank changes so page, tab, and provenance state cannot cross bank boundaries.
• Validate ?page= against the loaded bank tree before requesting it.
• Fall back to the first page when the requested ID is invalid for the current bank.
• Add unit coverage for valid, missing, folder, and absent page parameters.

Verification

• TZ=UTC npm test (158 tests)
• npm run build
• ./scripts/hooks/lint.sh
• ./scripts/hooks/check-unused.sh (advisory; no new findings)
• Headless browser network QA:
  • switching between populated banks produced no failed API requests
  • a foreign-bank ?page= produced no 404 and opened the current bank's first page
  • a valid ?page= requested and opened the specified page with HTTP 200

Fixes #3807

[strix-security]

Strix Security Review

No security issues found.

_{Updated for 54c05ae.}

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