LeanHttp 0.3.0

Added

• Inductive absolute/relative Target values, RelativeRef, checked target!
  literals, dynamic target parsing, and pure resolution with typed errors.
• Relative paths, directory merging, dot-segment removal, and explicit omitted
  versus empty query semantics for session base URIs.
• requestAsync and requestAsAsync integration with Std.Async, using a
  dedicated worker and session for each one-shot request.
• requestAsTask and bounded batch APIs: requestManyTask, requestManyAsTask,
  requestManyAsync, and requestManyAsAsync.
• A strictly positive Concurrency type and Batch.Config. Batch workers reuse
  their own sessions, consume a shared queue, and preserve input result order.
• Optional session configuration for request, requestAs, and requestTask.
• A design proposal covering target semantics, async scheduling, ownership,
  timeout behavior, cancellation limits, and future backend choices.
• Regression tests for target resolution, async overlap, concurrency bounds,
  connection reuse, result ordering, independent failure handling, and loader
  failures in batches.

Changed

• Request.uri now has type Target. Existing URI arguments coerce to
  .absolute; code inspecting the field must handle the two target cases or
  resolve it first. Response.effectiveUri remains a Std.Http.URI.
• Request constructors and URI-taking request helpers accept Target.
• Absolute requests must have an HTTP(S) scheme, authority, and an empty or
  slash-prefixed path. They no longer inherit the base merely because an
  authority was absent. Use an explicit
  relative target for base-URI requests. Scheme-relative //host/path targets
  are rejected; changing authority requires an explicit absolute URI.
• The package version and default user agent are now 0.3.0 and leanhttp/0.3.0.

Async behavior

• Transfers use blocking libcurl on dedicated threads. Async waits suspend
  through Lean's task scheduler; batches bound worker threads and sessions.
• Timeouts start at transfer execution, excluding batch queue time.
• Dropping a task or abandoning an async branch does not cancel a transfer.
  Workers close their sessions after completion or timeout. Persistent pools,
  streaming, and transfer cancellation are deferred.