feat(cli): HF_TOOL_CONTEXT artifact events and project lock for agent harnesses (#5520)

* feat(cli): HF_TOOL_CONTEXT artifact events and project lock for agent harnesses

* fix(cli): serialize stale project lock takeover

Use a short-lived break lock so only one waiter can remove a dead
holder's lock. Cover the contention path with six real processes.

* fix(cli): hold snapshot lock through finalization

Keep the project lock while contact sheets, artifact events, and frame
descriptions read captured files so another snapshot cannot replace them.

* fix(cli): recover a project lock after the breaker crashes

A killed takeover left project.lock.break in place, so later commands
waited out the timeout even though both holders were dead. Reclaim that
file only when its recorded process is dead, and compare artifact paths
after the platform resolves them.

* fix(cli): accept a killed breaker process with no signal name

Windows ends the process without reporting SIGKILL, so the regression
was failing before it checked that the leftover breaker can be reclaimed.

* fix(cli): leave a killed project-lock breaker in place

Reclaiming a dead breaker unlinks a name another process may just have
created, so two commands can hold the lock. The timeout names that file
and its pid and says to delete it to continue.

docs/docs.json

@@ -960,6 +960,7 @@
               "developers/cli",
               "packages/cli",
               "developers/catalog-search",
+              "developers/harness-tool-context",
               "packages/lint"
             ]
           },