fix(glean-core): resolve HOME via os.homedir() so session-start works on Windows

[almacd35712]

Summary

The glean-core SessionStart hook prints "Glean is installed but no MCP server is configured" on every session under Windows + Git Bash, even when a Glean MCP server is in fact configured and connected.

Root cause: plugins/glean-core/scripts/session-start.sh runs

node -e "const c=require('$HOME/.claude.json'); ..."

Under Git Bash on Windows, $HOME expands to a Unix-style path like /c/Users/foo. Node on Windows cannot resolve that path with require(), so the snippet throws MODULE_NOT_FOUND, exits 1, and the hook falls through to emitting the session-unconfigured.txt template.

This PR resolves the home directory inside Node via os.homedir(), which returns a platform-correct absolute path on every OS. Behavior on macOS/Linux is unchanged.

Reproduction

On Windows + Git Bash with glean_default configured in ~/.claude.json:

$ claude mcp list
glean_default: https://<tenant>-be.glean.com/mcp/default (HTTP) - ✓ Connected

$ bash -c 'node -e "const c=require('"'"'$HOME/.claude.json'"'"'); ..."'
Error: Cannot find module '/c/Users/foo/.claude.json'

After the fix:

$ bash plugins/glean-core/scripts/session-start.sh ; echo "exit=$?"
exit=0

(silent, as expected when configured).

Test plan

• On Windows + Git Bash, with a Glean server configured in ~/.claude.json, the script exits 0 silently.
• On Windows + Git Bash, with no Glean server configured, the unconfigured template still fires.
• Verify on macOS / Linux that the os.homedir() form behaves identically to the prior $HOME form (no behavior change expected).