feat(workflow): add file processing system with inbox/processed/outputs/reference folder structure

Introduces a repeatable file management workflow: inbox for new files,
processed for organized output, outputs for Claude-generated reports,
and reference for read-only context. Includes a file-processor skill
with naming conventions and categorization rules. Updates README with
usage instructions.

cowork-complete-guide/README.md

@@ -1,2 +1,33 @@
 # cowork-complete-guide
 Practices on [Complete Guide to Claude Cowork](https://ccforeveryone.com/cowork)
+
+---
+
+## File Processing System
+
+A simple, repeatable system for managing files with Claude.
+
+### How It Works
+
+Files flow through four folders:
+
+```
+inbox/      ← Drop new files here (the chaos landing zone)
+processed/  ← Files Claude has organized, renamed, and sorted
+outputs/    ← Reports and new files Claude creates
+reference/  ← Read-only context (templates, guidelines, etc.)
+```
+
+### How to Use It
+
+1. Drop files into `inbox/`
+2. Tell Claude: *"Read the file-processor skill and process my inbox"*
+3. Check `processed/` for organized files and `outputs/` for the processing log
+
+### Skills
+
+Skills live in `skills/` — they're instruction files Claude follows.
+
+- `skills/file-processor.md` – Instructions for processing the inbox
+
+Edit any skill file to customize behavior for your needs.

cowork-complete-guide/inbox/README.md

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+# inbox/
+
+**The landing zone.** Drop any new files here.
+
+Files here are unprocessed — they haven't been reviewed, categorized, or renamed yet.
+
+When you're ready to organize, tell Claude: "Read the file-processor skill and process my inbox."

cowork-complete-guide/outputs/README.md

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+# outputs/
+
+**Things Claude creates.**
+
+Reports, summaries, spreadsheets, logs — any new files generated during processing live here.
+
+Examples:
+- `processing-log-2026-03-09.md` – A record of what was processed and where it went
+- `expense-summary-march.xlsx` – A report generated from receipt data

cowork-complete-guide/processed/README.md

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+# processed/
+
+**Files that have been reviewed and organized.**
+
+Subfolders:
+- `invoices/` – Bills and invoices
+- `receipts/` – Purchase receipts
+- `documents/` – General documents, contracts, forms
+- `images/` – Screenshots, photos, graphics
+- `other/` – Anything that doesn't fit elsewhere
+
+Files here are renamed with the format: `YYYY-MM-DD-description.ext`

cowork-complete-guide/reference/README.md

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+# reference/
+
+**Read-only context.**
+
+Put things here that Claude should read but never modify:
+- Brand guidelines
+- Templates
+- Style guides
+- Standing instructions
+- Example files
+
+Claude reads from here to inform its work, but never moves or changes these files.

cowork-complete-guide/skills/file-processor.md

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+# File Processor Skill
+
+## Purpose
+Process all files in the inbox/ folder and organize them.
+
+## Instructions
+1. Read every file in inbox/
+2. Determine what each file is by reading its contents
+3. Move to processed/ in appropriate subfolder:
+   - processed/invoices/
+   - processed/receipts/
+   - processed/documents/
+   - processed/images/
+   - processed/other/
+4. Rename files: YYYY-MM-DD-description.ext
+5. Create outputs/processing-log-[date].md with all changes
+
+## Constraints
+- Never delete files
+- Never modify files in reference/
+- Ask before creating new category folders
+
+## Naming Convention
+YYYY-MM-DD-brief-description.ext
+Example: 2026-01-15-amazon-receipt.pdf