Add precc-token-saver

[yijunyu]

Adds precc-token-saver (universal, crates = ["*"]).

$ cargo agents plugin validate <repo-root>
✅ precc-token-saver/SYMPOSIUM.toml (plugin)
    ✅ precc-token-saver/SKILL.md (skill)

Mirror: https://github.com/peria-ai/precc-symposium-plugin

[yijunyu]

Friendly ping on this one — no rush if it's just in the queue. The plugin + skill still validate clean:

✅ precc-token-saver/SYMPOSIUM.toml (plugin)
    ✅ precc-token-saver/SKILL.md (skill)

Happy to adjust anything that'd help it land — otherwise it's ready whenever you are. Thanks for maintaining the feed! 🙏