refactor(cli): change from env var injection to direct prompt concatenation

- Replace $PROTO/$TMPL environment variable injection with systemRules/roles direct concatenation
- Append rules to END of prompt instead of prepending
- Change prompt field name from RULES to CONSTRAINTS in all prompts
- Default to universal-rigorous-style template when --rule not specified
- Update all .claude documentation, agents, commands, and skills
- Add streaming_content type support for Gemini delta messages

Breaking: Prompts now use CONSTRAINTS field instead of RULES

.claude/commands/issue/discover-by-prompt.md

@@ -267,7 +267,7 @@ EXPECTED: JSON exploration plan following exploration-plan-schema.json:
   "estimated_iterations": N,
   "termination_conditions": [...]
 }
-RULES: $PROTO | Use ACE context to inform targets | Focus on actionable plan
+CONSTRAINTS: Use ACE context to inform targets | Focus on actionable plan
 `;
 
 // Step 3: Execute Gemini planning

.claude/commands/issue/plan.md

@@ -131,7 +131,7 @@ TASK: • Analyze issue titles/tags semantically • Identify functional/archite
 MODE: analysis
 CONTEXT: Issue metadata only
 EXPECTED: JSON with groups array, each containing max 4 issue_ids, theme, rationale
-RULES: $PROTO | Each issue in exactly one group | Max 4 issues per group | Balance group sizes
+CONSTRAINTS: Each issue in exactly one group | Max 4 issues per group | Balance group sizes
 
 INPUT:
 ${JSON.stringify(issueSummaries, null, 2)}