docs: reorganize tree, restore architecture + research from archive, add Phase 0 reports

Active docs/ was stub scaffolding while the real docs sat in docs/_archive/.
Restore and correct them, and record the Phase 0 work.

- docs/architecture/current.md: verified system map (from archived SYSTEM_OVERVIEW,
  9 corrections against code).
- docs/research/competitors.md: sourced competitor analysis (from archived
  PRODUCT_RESEARCH, feature matrix corrected).
- docs/decisions/ADR-002-job-application-model.md: the Job/JobApplication split.
- docs/application-discovery-report.md, docs/implementation-roadmap.md,
  docs/phase-0-foundation-report.md, docs/career-workspace-branch-assessment.md.
- Remove 10 zero-byte placeholder files that advertised content that never existed.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

docs/ai/prompts.md

@@ -0,0 +1,51 @@
+# AI Prompt Management
+
+## Purpose
+
+Centralise prompts.
+
+Avoid random prompts scattered throughout code.
+
+---
+
+# Requirements
+
+Prompts should:
+
+- Be version controlled.
+- Be documented.
+- Have tests where possible.
+
+---
+
+# Prompt Structure
+
+Every prompt should define:
+
+Purpose.
+
+Inputs.
+
+Expected output.
+
+Restrictions.
+
+---
+
+# Example
+
+Task:
+
+Improve CV bullet point.
+
+Input:
+
+Existing bullet.
+
+Output:
+
+Improved bullet.
+
+Restrictions:
+
+Do not add unsupported achievements.