chore: harden independent release workflow

[tisonkun]

Summary

• Update anyhow to 1.0.104, resolving RUSTSEC-2026-0190.
• Release exn and exn-anyhow independently with package-specific commit and tag conventions.
• Add the strict docs.rs-style build from fast/template to cargo x lint and fix the broken ErrorExt::raise rustdoc link.

Release behavior

• cargo release minor -p exn plans exn 0.4.0 with tag v0.4.0.
• cargo release minor -p exn-anyhow plans exn-anyhow 0.2.0 with tag exn-anyhow-v0.2.0.
• consolidate-commits = false ensures each package's release commit template is honored.
• dependent-version = "upgrade" updates the workspace dependency after releasing exn; exn-anyhow can then be released separately.

The intended order is exn first, followed by exn-anyhow.

Validation

• cargo x lint
• cargo x test --no-capture
• cargo x build --locked
• cargo deny check advisories
• Independent cargo release minor -p <crate> --no-confirm dry runs
• Full no-publish/no-push release sequence in a temporary clone