Make progress logging MANDATORY for the coding agent during implementation, enforced by the MCP server via plan.md.

## Problem

Currently, progress.txt shows mostly entries from k4000 (automatic system events), but very few entries from the coding agent itself. When an agent starts with a fresh context, it's hard to understand what was actually done during implementation.

This is a problem across **all projects** using k4000-mcp, not just this one. The behavior needs to be enforced by the MCP server so it applies universally.

Example of current progress.txt (mostly k4000 entries):
```
[2026-01-08T11:48:53Z] [k4000] Task created
[2026-01-08T11:49:22Z] [k4000] Task analysis started
[2026-01-08T11:49:51Z] [k4000] 6 features saved to feature-list.json
[2026-01-08T11:50:05Z] [k4000] 6 questions generated, awaiting answers
[2026-01-08T11:57:05Z] [k4000] Question q1 answered
[2026-01-08T11:59:11Z] [k4000] Status changed: ready -> implementing
```

What we want (more agent entries):
```
[2026-01-08T11:48:53Z] [k4000] Task created
...
[2026-01-08T11:59:11Z] [k4000] Status changed: ready -> implementing
[2026-01-08T12:00:00Z] [claude] [F1] Starting storage layer implementation
[2026-01-08T12:15:00Z] [claude] [F1] Added StateManager struct to src/storage.rs
[2026-01-08T12:30:00Z] [claude] [F1] Implemented save/load methods
[2026-01-08T12:45:00Z] [claude] [F1] Tests passing, storage layer complete
[2026-01-08T13:00:00Z] [claude] [F2] Starting API endpoint implementation
...
```

## Solution

Add a **mandatory section** to every task's `plan.md` that instructs the agent to log progress. Since the agent reads plan.md when working on a task, this ensures the instruction persists across context windows.

### Implementation

1. **Update plan.md template**: Add a mandatory "Progress Logging Requirements" section to the plan.md structure that K4000 generates via `update_task_plan`.

2. **Include in plan.md structure** (in CLAUDE.md): Update the documented plan.md template to include the mandatory logging section.

3. **The section should include**:
   - Clear statement that progress logging is MANDATORY
   - When to log (starting feature, code changes, completing feature, blockers, decisions)
   - How to log (`log_progress` tool with examples)
   - Warning that features may be rejected if no progress logs exist

### Example plan.md section to add:

```markdown
## MANDATORY: Progress Logging

You MUST log progress during implementation using `log_progress`. This is required for context restoration when starting fresh sessions.

**When to log:**
- Starting work on a feature: `log_progress(feature_id="F1", message="Starting API endpoint implementation")`
- Significant code changes: `log_progress(feature_id="F1", message="Added auth middleware to src/auth.rs")`
- Completing a feature: `log_progress(feature_id="F1", message="Feature complete, tests passing")`
- Blockers or issues: `log_progress(message="Blocked: need database migration first")`
- Important decisions: `log_progress(feature_id="F2", message="Chose JWT over session tokens for stateless auth")`

**Frequency:** Log at least once per significant code change or every 15-20 minutes of work.
```

## Key Principle

The plan.md is the persistent "instructions" document that agents read. By including mandatory logging requirements in every plan.md, we ensure ALL projects using k4000-mcp get this behavior - regardless of their CLAUDE.md content.

## Acceptance Criteria

- The plan.md template in CLAUDE.md includes a mandatory progress logging section
- When `update_task_plan` is called, the response/documentation guides inclusion of this section
- The section clearly states logging is MANDATORY (not optional)
- The section includes examples of when/how to log
- This applies to ALL projects using k4000-mcp, regardless of their CLAUDE.md content
