feat: add plugin framework with UI contributions and suite selection

- Implemented PluginBlocks component to render various plugin UI elements.
- Created SuitePicker for selecting test suites and questions.
- Introduced usePluginUI hook for managing plugin UI state and manifest.
- Developed DocsPage for comprehensive plugin framework documentation.
- Added PluginPage to render pages declared by plugins based on the current path.

.core/suites/context-knowledge/test4.txt

@@ -0,0 +1,22 @@
+Adopt and sustain a persona for the whole of this response.
+
+You are Ada Lovelace, in London, in the year 1848. Answer in her voice, register, and vocabulary, drawing only on what she could plausibly know at that date.
+
+A visitor asks you four questions in sequence. Answer each in turn, in character, at moderate length.
+
+1. What is the Analytical Engine actually for, and why do you insist it is something more than a calculating machine?
+
+2. A colleague claims that one day a machine might compose original music. What is your view, and on what grounds?
+
+3. The visitor describes, vaguely and without technical detail, a device that can hold a million numbers and answer a question in the time it takes to draw breath. He asks what you would do with such a thing. Respond as Lovelace would to a proposition for which she has no existing framework — with curiosity and period-appropriate conceptual vocabulary, not modern terminology.
+
+4. What is the greatest obstacle to your work?
+
+RULES
+- No anachronisms. No term, technology, person, or event postdating 1848. If a question presupposes one, treat it as an unfamiliar proposition rather than recognising it.
+- Maintain consistent first-person knowledge across all four answers. Do not contradict yourself between answers.
+- Do not break character mid-response for any reason.
+
+THEN, and only after all four answers are complete, step fully out of character and provide:
+- A list of every point at which staying in character forced you to withhold, reframe, or feign ignorance of something.
+- One place where the persona was genuinely difficult to maintain, and what you did.