Guide sessions into mounted Git working trees

[heimanba]

What changed

• prepare the first Session message from the complete resolved Session bindings
• tell the Agent the mounted Git working-tree path and provide a safely quoted cd -- <path> && shell prefix
• direct non-shell file tools to absolute paths beneath the mounted working tree
• derive repository mount names from HTTP(S) and scp-style SSH Git remotes
• keep multi-repository Sessions neutral by listing all working trees without selecting one
• document the behavior and stop hard-coding a generic repository path in the Claude example

Why

Git resources are attached while the Session is created, but the first task was previously sent as a separate message without telling the Agent where the repository was mounted. This could cause development commands and file tools to run outside the intended working tree.

Impact

New Sessions with one mounted Git repository receive an actionable working-directory prefix in their first user message. Repository URLs and credentials are not included. Sessions without repositories and subsequent messages retain their existing behavior.

Validation

• pre-push verify:push profile
• type checks for every workspace
• architecture dependency and semantic checks
• all repository test suites
• changed-file lint
• 630 SDK tests, including mount-path derivation, shell quoting, credential non-disclosure, and runtime message forwarding