fix(bazel): replace askama templates with include_str! in memories (#11778)

## Summary

- The experimental Bazel CI builds fail on all platforms because askama
resolves template paths relative to `CARGO_MANIFEST_DIR`, which points
outside the Bazel sandbox. This produces errors like:
  ```
error: couldn't read
`codex-rs/core/src/memories/../../../../../../../../../../../work/codex/codex/codex-rs/core/templates/memories/consolidation.md`:
No such file or directory
  ```
- Replaced `#[derive(Template)]` + `#[template(path = "...")]` with
`include_str!` + `str::replace()` for the three affected templates
(`consolidation.md`, `stage_one_input.md`, `read_path.md`).
`include_str!` resolves paths relative to the source file, which works
correctly in both Cargo and Bazel builds.
- The templates only use simple `{{ variable }}` substitution with no
control flow or filters, so no askama functionality is lost.
- Removes the `askama` dependency from `codex-core` since it was the
only crate using it. The workspace-level dependency definition is left
in place.
- This matches the existing pattern used throughout the codebase — e.g.
`codex-rs/core/src/memories/mod.rs` already uses
`include_str!("../../templates/memories/stage_one_system.md")` for the
fourth template file.

## Test plan

- [ ] Verify Bazel (experimental) CI passes on all platforms
- [ ] Verify rust-ci (Cargo) builds and tests continue to pass
- [ ] Verify `cargo test -p codex-core` passes locally

codex-rs/Cargo.lock

@@ -458,58 +458,6 @@ dependencies = [
  "term",
 ]
 
-[[package]]
-name = "askama"
-version = "0.15.4"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "08e1676b346cadfec169374f949d7490fd80a24193d37d2afce0c047cf695e57"
-dependencies = [
- "askama_macros",
- "itoa",
- "percent-encoding",
- "serde",
- "serde_json",
-]
-
-[[package]]
-name = "askama_derive"
-version = "0.15.4"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "7661ff56517787343f376f75db037426facd7c8d3049cef8911f1e75016f3a37"
-dependencies = [
- "askama_parser",
- "basic-toml",
- "memchr",
- "proc-macro2",
- "quote",
- "rustc-hash 2.1.1",
- "serde",
- "serde_derive",
- "syn 2.0.114",
-]
-
-[[package]]
-name = "askama_macros"
-version = "0.15.4"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "713ee4dbfd1eb719c2dab859465b01fa1d21cb566684614a713a6b7a99a4e47b"
-dependencies = [
- "askama_derive",
-]
-
-[[package]]
-name = "askama_parser"
-version = "0.15.4"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "1d62d674238a526418b30c0def480d5beadb9d8964e7f38d635b03bf639c704c"
-dependencies = [
- "rustc-hash 2.1.1",
- "serde",
- "serde_derive",
- "unicode-ident",
- "winnow",
-]
-
 [[package]]
 name = "asn1-rs"
 version = "0.7.1"
@@ -1662,7 +1610,6 @@ version = "0.0.0"
 dependencies = [
  "anyhow",
  "arc-swap",
- "askama",
  "assert_cmd",
  "assert_matches",
  "async-channel",