Export WARP_SKILL_DIRS as absolute paths to the agent shell

[warp-agent-staging]

Description

WARP_SKILL_DIRS is injected into a Factory agent's environment holding paths relative to the environment working directory (e.g. factory-dev/frank/agents/implementation/skills,factory-dev/frank/skills). The driver's own skill loader already resolves these against working_dir, but the raw relative value also leaks into the agent's shell, where skills read it directly — for example the github skill's sed/cd snippet that parses WARP_SKILL_DIRS to locate the factory's factory.yaml and resolve the factory name/alias.

Agents routinely cd into a product repo. Once they do, the relative entries resolve against the wrong directory, sed reads nothing, and skill resolution silently yields empty strings — producing a bare factory label or a missing footer (SEV2, warpdotdev/warp-server#15372).

The environment working directory is only known absolutely on the client (the server injects a relative value because it cannot know the sandbox mount path). So this fixes it at the authoritative place that can resolve it: AgentDriver::new re-exports an absolute WARP_SKILL_DIRS into the agent's environment, resolved against working_dir. Because this value flows through the terminal driver and the third‑party harness runners, Oz, Claude, and Codex agents all see absolute paths regardless of their current working directory. The server-side relative value and the driver's own loader are left unchanged.

Linked Issue

warpdotdev/warp-server#15372

• The linked issue is labeled ready-to-spec or ready-to-implement.
• Where appropriate, screenshots or a short video of the implementation are included below (especially for user-visible or UI changes).

Changes

• Added a pure absolute_skill_dirs(working_dir, dirs) helper in app/src/ai/agent_sdk/driver.rs that resolves relative entries against working_dir (absolute entries pass through) and re-joins them. absolute_skill_dirs_env is now a thin env-reading wrapper over it.
• The value is assembled directly as an OsString from each path's raw OsStr bytes — not via to_string_lossy — so a working_dir containing non-UTF-8 bytes (possible on Unix) is preserved verbatim instead of being corrupted with U+FFFD.
• AgentDriver::new inserts that absolute value into the agent's resolved env vars, overriding the relative value inherited from the environment. Returns None/no-op when WARP_SKILL_DIRS is unset or empty.

Testing

Non-UI change (environment-variable resolution), so no visual proof applies.

Regression tests in app/src/ai/agent_sdk/driver_tests.rs (all drive the pure helper with PathBuf inputs — no global set_var/remove_var, no serial):

• absolute_skill_dirs_makes_relative_entries_absolute — a relative value like the reported one becomes absolute (joined onto the working dir), which is exactly what makes the shell snippet resolve from any cwd.
• absolute_skill_dirs_passes_absolute_entries_through — absolute entries are untouched; only relative ones are joined.
• absolute_skill_dirs_empty_is_none — empty input leaves the variable untouched.
• absolute_skill_dirs_preserves_non_utf8_working_dir (cfg(unix)) — a non-UTF-8 working dir keeps its raw 0xff byte with no U+FFFD replacement sequence.

Commands run (in warp/):

• cargo test -p warp --lib absolute_skill_dirs → 4 passed; 0 failed

• cargo check -p warp --lib → clean

• ./script/format and cargo fmt -p warp -- --check → clean

• cargo clippy -p warp --lib → clean

• I have manually tested my changes locally with ./script/run

Agent Mode

• Warp Agent Mode - This PR was created via Warp's AI Agent Mode

This PR was created by Oz (running Codex).