…der_rag (BREAKING)

Published `aprender-rag = "0.31.2"` had `[lib] name = "trueno_rag"`,
making `use aprender_rag::*` not compile against external consumers.
This renames the lib to match the package name + bumps to v0.32.0
(breaking import-path change requires minor version bump per SemVer).

## Why

When operators add `aprender-rag = "0.31.2"` to Cargo.toml, the
natural Rust import is `use aprender_rag::*`. The published lib
exposed `use trueno_rag::*` instead — the historical pre-monorepo
crate name leaked through.

## What ships

- `crates/aprender-rag/Cargo.toml`: `[lib] name = "trueno_rag"` →
  `"aprender_rag"`.
- `crates/aprender-rag/src/**/*.rs`: doctests
  `use trueno_rag::*` → `use aprender_rag::*` (Rust source only;
  the historical-link string `paiml/trueno-rag` in `repository:` is
  preserved for backward compatibility).
- `crates/aprender-rag/crates/trueno-rag-cli/`: sub-cli's
  `Cargo.toml` and `src/*.rs` updated to consume the renamed lib
  (declared as `aprender-rag = { path = "../..", version = "0.32.0" }`,
  imports use `aprender_rag::*`).
- Workspace `version` 0.31.2 → 0.32.0 (touches 64 Cargo.toml + Rust
  files via consistent sed).

## What is NOT changed

- `crates/aprender-core`, `crates/aprender-train`, and
  `crates/aprender-orchestrate` continue to depend on the **external**
  `trueno-rag = "0.2"` crate from crates.io (NOT the local path
  dep). Their `use trueno_rag::*` imports remain — they consume a
  separate, older published crate. Migrating those workspace crates
  to the local `aprender-rag` is a separate, larger refactor (out
  of scope for this PR).
- `apr-cli/src/commands/mono.rs` line 184 already declared the
  intended lib name `aprender_rag` for the `apr mono` rename
  registry — this PR makes the Cargo.toml match the registry.

## Verification

  $ cargo check -p aprender-rag             # ✓ clean
  $ cargo test -p aprender-rag --lib        # 442/442 pass
  $ cargo test -p aprender-rag --doc        # 5/5 pass

  $ cargo check --workspace                 # 1 pre-existing error in
                                              aprender-orchestrate bin
                                              (batuta::cmd_code arg
                                              count drift; unrelated to
                                              this PR — verified by
                                              reproducing on main pre-
                                              this-branch via git
                                              stash).

## Five Whys

1. Why did the lib name drift from the package name? Pre-monorepo
   the crate was published as `trueno-rag` with lib name
   `trueno_rag`; the APR-MONO consolidation renamed the package
   to `aprender-rag` but didn't update the lib name (the file lives
   inside `crates/aprender-rag/Cargo.toml` but `[lib] name = "trueno_rag"`).
2. Why did external consumers notice but internal tests not? Doctests
   inside aprender-rag use `use trueno_rag::*` (matching the lib
   name) — they pass internally because the lib IS named `trueno_rag`.
   External consumers expect `use aprender_rag::*` (matching the
   package name they typed in Cargo.toml).
3. Why bump to 0.32.0 (minor) not 0.31.3 (patch)? Renaming the lib
   changes the public import path, which is a breaking API change
   per SemVer. Patch bumps must be backward-compatible; this is not.
4. Why not also migrate workspace crates off external `trueno-rag = "0.2"`?
   Out of scope. The external crate still publishes; migrating
   internal consumers requires API-diff investigation between the
   published 0.2.x and the local 0.32.0 (different feature surfaces,
   different traits). Tracked as a separate refactor.
5. Why ship even though `aprender-orchestrate` has a pre-existing
   build error? The error is in the `aprender-orchestrate` bin's
   call to `batuta::agent::code::cmd_code` — unrelated to the rag
   lib name. Pre-existing on main (verified via `git stash` +
   `cargo check`). Blocking this PR on it would conflate unrelated
   defects.

## Operator follow-up

`cargo publish` requires operator credentials. After this PR merges:
  cd /home/noah/src/aprender
  cargo publish -p aprender-rag       # publishes 0.32.0
  cargo install aprender --force      # post-publish QA per
                                        feedback_post_publish_qa_required.md

This addresses the user-reported defect: "the published
aprender-rag = "0.31.2" still has [lib] name = "trueno_rag" in its
Cargo.toml, so use aprender_rag::* won't actually compile against
the current crate."

Refs: feedback_post_publish_qa_required.md (yank-on-skip rule)

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>