consolidate: unify all config/data paths to ~/.codecora/cora-code/

[ajianaz]

Problem

cora-code currently scatters data across 3+ locations:

Data	Current Path	Source
Config + Auth	~/.cora/	config/loader.rs::cora_dir()
Review cache	~/.cache/cora/reviews/	engine/cache.rs::cache_dir()
Graph DB + update cache	~/.codecora/cora-code/ ✅	data_dir.rs::cora_data_dir()

This is confusing for users (where is my config?), complicates backups, and fragments the data directory structure.

Proposed Solution

Consolidate all paths to ~/.codecora/cora-code/:

~/.codecora/cora-code/
├── config.yaml        (was ~/.cora/config.yaml)
├── auth.toml          (was ~/.cora/auth.toml)
├── cora.db            (already here ✅)
├── update-cache.json  (already here ✅)
└── cache/
    └── reviews/       (was ~/.cache/cora/reviews/)

Note: .cora/history/ remains project-local (per-repo, not global).

Migration

Auto-migrate old paths on first run:

1. Check if ~/.cora/config.yaml exists and new path doesn't → copy
2. Check if ~/.cora/auth.toml exists and new path doesn't → copy
3. Check if ~/.cache/cora/reviews/ exists → move to new path
4. Print info log: "Migrated config from ~/.cora/ to ~/.codecora/cora-code/"
5. Do NOT delete old files (user can clean up manually)

Scope

• Update cora_dir() in loader.rs → use data_dir::cora_data_dir()
• Update cache_dir() in cache.rs → use data_dir::cora_data_dir().join("cache/reviews")
• Add migration logic in loader.rs
• Update all user-facing strings ("/.cora/" → "/.codecora/cora-code/")
• Update docs/README references