refactor(renderer): refactor renderer in multiple files

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[Copilot]

Pull request overview

This PR refactors the UI renderer into smaller modules (events/buffer/context) and updates RenderState’s indexing strategy, with corresponding test updates to use the new structure.

Changes:

• Split renderer responsibilities into renderer.events, renderer.buffer, and a shared singleton renderer.ctx.
• Replace RenderState’s per-line index with sorted range arrays and add a cached max-line optimization.
• Add batch update support in output_window to reduce repeated modifiable toggling during multi-step buffer updates.

Reviewed changes

Copilot reviewed 16 out of 16 changed files in this pull request and generated 5 comments.

Show a summary per file

File	Description
tests/unit/render_state_spec.lua	Updates assertions for new range-based validity flags and adds coverage for early-return paths.
tests/unit/permission_integration_spec.lua	Switches from renderer internals to renderer.events + renderer.ctx for integration-style behavior.
tests/unit/hooks_spec.lua	Routes hook tests through renderer.events handlers.
tests/unit/cursor_tracking_spec.lua	Updates scrolling tests to use ctx.prev_line_count and message update events.
tests/manual/renderer_replay.lua	Reads actions from renderer.ctx.render_state instead of renderer internals.
tests/helpers.lua	Captures actions via renderer.ctx.render_state.
lua/opencode/ui/renderer/events.lua	New module containing renderer event handlers (message/part/session/permission/question/etc.).
lua/opencode/ui/renderer/ctx.lua	New shared mutable renderer context (singleton via require cache).
lua/opencode/ui/renderer/buffer.lua	New module encapsulating buffer writes, diff-optimized part replacement, and rerender helpers.
lua/opencode/ui/renderer.lua	Becomes orchestrator: subscriptions, reset/teardown, full-session render, scrolling, and public accessors.
lua/opencode/ui/render_state.lua	Replaces line index maps with sorted ranges + binary search; adds snapshot-id index + max-line caching.
lua/opencode/ui/question_window.lua	Calls question rendering/clearing via renderer.events.
lua/opencode/ui/permission_window.lua	Calls permissions rendering via renderer.events.
lua/opencode/ui/output_window.lua	Adds begin_update/end_update batching and updates buffer validity checks.
lua/opencode/ui/debug_helper.lua	Uses renderer.ctx.render_state for message lookup.
lua/opencode/state.lua	Removes legacy wrapper module file (module now resolves via opencode/state/init.lua).

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