docs(install): warn about multiple distribution channels (#314)

[ajianaz]

Summary

Fixes #314 — install instructions don't warn about multiple distribution channels causing PATH conflicts.

The install docs listed several methods (installer script, cargo, pre-built binaries, npm) without warning that having more than one on $PATH silently resolves to whichever appears first. On a real developer machine three copies were present simultaneously (~/.local/bin/cora, ~/.cargo/bin/cora, ~/.bun/bin/cora) and the stale npm v0.2.4 was being invoked, causing confusing behavior with no warning.

Closes #315 as a duplicate of #314 (same title, body, author, opened 3 seconds apart — already closed on the issue tracker).

Changes

README.md — Install section

• Replaces the bare install commands with a short table recommending one install method per use case (installer script / cargo / pre-built binaries).
• Adds a "Verify which cora you're running" snippet using which -a cora (lists every cora on PATH) and cora --version.
• Explains what to do when more than one entry appears (remove the unwanted one, or reorder PATH).
• Cross-links issue docs: install instructions don't warn about multiple distribution channels causing PATH conflicts #314 for background.

CHANGELOG.md

Entry under ## [0.6.1] -> Changed — Docs.

Tests

Docs-only change. cargo build and cargo fmt --check still pass to keep the version bump consistent with the rest of the 0.6.1 patch bundle.

Versioning

Patch bump 0.6.0 → 0.6.1 (shares the release with #316, #312, #313).

⚠️ Merge note: CHANGELOG and Cargo.toml will conflict with #317, #318, and #319. Suggested merge order: #317 → #318 → #319 → this PR (docs last). Conflicts are confined to the ## [0.6.1] block of CHANGELOG.md and the version line in Cargo.toml/Cargo.lock.

Checklist

• cargo build passes
• cargo fmt --check clean
• CHANGELOG entry under ## [0.6.1] → ### Changed — Docs
• Version bumped in Cargo.toml + Cargo.lock
• Duplicate issue docs: install instructions don't warn about multiple distribution channels causing PATH conflicts #315 closed as not-planned