feat: gated project experience & prompt intelligence

Implements the full gated session flow and prompt intelligence system:

- Prisma schema: add gated, priority, summary, chapters, linkTarget fields
- Session gate: state machine (gated → begin_session → ungated) with LLM-powered
  tool selection based on prompt index
- Tag matcher: intelligent prompt-to-tool matching with project/server/action tags
- LLM selector: tiered provider selection (fast for gating, heavy for complex tasks)
- Link resolver: cross-project MCP resource references (project/server:uri format)
- Prompt summary service: LLM-generated summaries and chapter extraction
- System project bootstrap: ensures default project exists on startup
- Structural link health checks: enrichWithLinkStatus on prompt GET endpoints
- CLI: create prompt --priority/--link, create project --gated/--no-gated,
  describe project shows prompts section, get prompts shows PRI/LINK/STATUS
- Apply/edit: priority, linkTarget, gated fields supported
- Shell completions: fish updated with new flags
- 1,253 tests passing across all packages

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

src/db/prisma/migrations/20260225220000_add_gated_prompt_priority_summary_link/migration.sql

@@ -0,0 +1,11 @@
+-- AlterTable: Add gated flag to Project
+ALTER TABLE "Project" ADD COLUMN "gated" BOOLEAN NOT NULL DEFAULT true;
+
+-- AlterTable: Add priority, summary, chapters, linkTarget to Prompt
+ALTER TABLE "Prompt" ADD COLUMN "priority" INTEGER NOT NULL DEFAULT 5;
+ALTER TABLE "Prompt" ADD COLUMN "summary" TEXT;
+ALTER TABLE "Prompt" ADD COLUMN "chapters" JSONB;
+ALTER TABLE "Prompt" ADD COLUMN "linkTarget" TEXT;
+
+-- AlterTable: Add priority to PromptRequest
+ALTER TABLE "PromptRequest" ADD COLUMN "priority" INTEGER NOT NULL DEFAULT 5;