feat(codex): nudge Gortex MCP read tools toward compressed reads

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Summary

• Add a dedicated Codex PreToolUse matcher for Gortex MCP read-shaped tools:
  mcp__gortex__read_file and mcp__gortex__get_editing_context.
• Route those Codex MCP read tool events through a Codex-specific soft-only handler.
• Reuse the existing gortexReadNudge compress-bodies guidance without adding new policy.
• Keep Codex MCP read guidance advisory-only: emit hookSpecificOutput.additionalContext; no permission decision, deny, input rewrite, or output suppression.

Design notes

• The Bash PreToolUse matcher remains separate from the MCP read-tool matcher.
• The Codex installer now manages two Gortex-owned PreToolUse entries: one for Bash and one for MCP read tools.
• Repeated apply remains idempotent; force refresh removes stale Gortex-owned PreToolUse entries and writes the two desired entries back.
• The MCP read-tool path intentionally does not call the generic runPreToolUse handler, so permissive permission_mode values cannot emit permissionDecision:"allow".
• Claude, Gemini, and Antigravity behavior remains unchanged.

Out of scope

• All other mcp__gortex__* tools
• PostToolUse MCP output
• apply_patch
• deny / enforcement behavior
• permission decisions
• input rewrite / updatedInput
• output suppression
• resolver / indexer / daemon / graph / MCP tool changes

Tests

• go test ./internal/agents/codex
• go test ./internal/hooks
• go test ./cmd/gortex
• git diff --check