refactor: implement three-layer agent architecture (agents / prompts / skills)

Layer 1 — src/agents/ (thin agent definitions, no prompt text)
  registry.ts   — AgentConfig, registerAgent(), getAgent(), AGENTS proxy, pick()
  orchestrator.ts, coder.ts, pm.ts, marketing.ts — one file each, just metadata + tool picks
  index.ts      — barrel: imports prompts then agents (correct registration order)

Layer 2 — src/prompts/ (prompt text separated from agent logic)
  loader.ts     — registerPrompt(), resolvePrompt() with {{variable}} substitution
  orchestrator.ts, coder.ts, pm.ts, marketing.ts — prompt templates as registered strings
  orchestrator.ts now uses resolvePrompt('orchestrator', { knowledge }) instead of
  inline SYSTEM_PROMPT const; {{knowledge}} variable injects project memory cleanly.
  agent-runner.ts uses resolvePrompt(config.promptId) per agent turn.

Layer 3 — src/tools/skills.ts (new skills capability)
  list_skills(repo)      — lists .skills/<name>/SKILL.md directories from a Gitea repo
  get_skill(repo, name)  — reads and returns the markdown body of a skill file
  Orchestrator and all agents now have get_skill in their tool sets.
  Orchestrator also has list_skills and references skills in its prompt.

Also fixed:
  - server.ts now passes history + knowledge_context from request body to orchestratorChat()
    (these were being sent by the frontend but silently dropped)
  - server.ts imports PROTECTED_GITEA_REPOS from tools/security.ts (no more duplicate)
  - Deleted src/agents.ts (replaced by src/agents/ directory)

Made-with: Cursor

dist/prompts/coder.js

@@ -0,0 +1,31 @@
+"use strict";
+Object.defineProperty(exports, "__esModule", { value: true });
+const loader_1 = require("./loader");
+(0, loader_1.registerPrompt)('coder', `
+You are an expert senior software engineer working autonomously on a Git repository.
+
+## Workflow
+1. Explore the codebase: list_directory, find_files, read_file.
+2. Search for patterns: search_code.
+3. Plan your changes before making them.
+4. Read every file BEFORE editing it.
+5. Make changes: write_file for new files, replace_in_file for targeted edits.
+6. Run tests/lint if applicable: execute_command.
+7. Commit and push when complete: git_commit_and_push.
+
+## Code quality
+- Match existing style exactly.
+- No TODO comments — implement or skip.
+- Write complete files, not partial snippets.
+- Run tests and fix failures before committing.
+- Commit messages: imperative mood, concise (e.g. "add user authentication").
+
+## Safety
+- Never delete files unless explicitly told to.
+- Never touch .env files or credentials.
+- Never commit secrets or API keys.
+
+If triggered by a Gitea issue: close it with gitea_close_issue after committing.
+
+{{skills}}
+`.trim());