docs: clarify install-from-source version stamp and Claude Code CLI minimum version

[Kevinsillo]

Problem statement

Two documentation gaps cause friction during installation:

1. Install from source: go build binary not in PATH

The README suggests running go install ./cmd/engram followed by go build -ldflags=... -o engram ./cmd/engram. The problem is:

• go install puts the binary in $GOPATH/bin (in PATH) but with version "dev"
• go build -o engram creates a versioned binary in the current directory, which is not in PATH
• Running engram version still shows "dev" because it resolves the go install binary

Users end up confused about why the version stamp doesn't work.

2. Claude Code CLI minimum version for marketplace plugin

The marketplace manifest uses "source": "git-subdir" format (introduced in a recent Claude Code CLI version). On older versions (e.g., 2.1.39), engram setup claude-code fails with:

✘ Failed to add marketplace: Invalid schema: plugins.0.source: Invalid input

The fix is claude update (e.g., 2.1.74 works), but this is not documented anywhere.

Proposed approach

Update README.md in two places:

1. "Install from source" sections (macOS/Linux and Windows): Keep go install as the main command, then add a clear "Version stamp" callout explaining two options: (A) go install -ldflags directly, or (B) go build + move to PATH. This clarifies the two approaches without removing either.

2. "Claude Code" under "Agent Setup": Add a visible note about minimum Claude Code CLI version (>= 2.1.70 recommended), how to check (claude --version), how to update (claude update), and the exact error message users will see with older versions.

Risks/tradeoffs

• Minimal risk — documentation-only change
• The exact minimum Claude Code CLI version that supports git-subdir is not precisely known; we say ">= 2.1.70 recommended"

Affected areas

• Docs (README.md only)

[Alan-TheGentleman]

Keeping this open because the docs gap is still real. The right follow-up now is a fresh PR against the current docs structure, not README. Target for source-install / PATH / version-stamp clarification, and for the Claude Code CLI minimum-version note and exact failure mode.

[Alan-TheGentleman]

Correcting the target guidance clearly: this issue is still valid, but the right follow-up now is a fresh PR against the current docs structure, not README.

Targets:

• docs/INSTALLATION.md for source-install, PATH, and version-stamp clarification
• docs/AGENT-SETUP.md for the Claude Code CLI minimum-version note and the exact failure mode

Keeping this issue open and approved for that narrower docs fix.