agents: record 2026-07-03 disk-space-cleanup session notes

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

Author: colonelpanic8

dotfiles/agents/skills/disk-space-cleanup/SKILL.md

@@ -182,6 +182,7 @@ Machine-specific heavy hitters seen in practice:
 - 2026-06-18 cleanup: deleting helper-validated Rust targets under `.worktrees/*/target` and `.claude/worktrees/*/target`, plus stale `~/Projects/lastfm-edit/target`, removed 24 target directories totaling 67.1G by helper sizing and moved `/` from 99% used to 90% used. Remaining large targets were top-level project caches under `keepbook`, `rlru`, `subtr-actor`, `rocket-sense`, `rocket-sense-pr-73-ci`, `rocket-sense-subtr-viewer`, `rocket-sense-controlled-plays`, and `boxcars`.
 - 2026-06-23 cleanup: deleting helper-validated Rust targets over 100M under `~/Projects` removed 21 target directories totaling 59.6G by helper sizing; `rocket-sense/.worktrees/missed-event-capture/target` was recreated once during verification and deleted again after no active Cargo/Rust process was found. Clearing rebuildable Cargo registry/git caches and removing stale `~/.rustup/toolchains/1.68.2-x86_64-unknown-linux-gnu` moved `/` from 99% used with 17G free to 91% used with 81G free. In this shell, `python`, `python3`, `cargo`, `rustup`, `ps`, and `cargo-sweep` were not on `PATH`; using `nix run nixpkgs#python3 -- ...` worked for the helper, and `nix shell nixpkgs#procps nixpkgs#ripgrep --command bash -lc 'ps ...'` worked for process checks.
 - 2026-06-28 cleanup: deleting helper-validated Rust targets over 500M under `~/Projects` removed 25 target directories totaling 102.6G by helper sizing and moved `/` from 98% used with 23G free to 86% used with 126G free. The largest wins were top-level `rlru`, `subtr-actor`, `rocket-sense`, `keepbook`, and `boxcars` targets plus many `rocket-sense` and `subtr-actor` `.worktrees/*/target` and `.claude/worktrees/*/target` directories. A follow-up scan over 100M found no remaining helper-validated Rust targets.
+- 2026-07-03 cleanup (from within a sandboxed agent shell): `sudo -n` was unavailable ("no new privileges" flag), so `sudo nix-collect-garbage -d`, `docker`/`podman` prune were all out. Sudo-free wins still worked: plain `nix-collect-garbage -d` talked to the daemon and freed 17.0 GiB (2777 store paths), and helper-validated Rust target deletions under `~/Projects` (`keepbook`, `rlru`, and several `rocket-sense/.claude/worktrees/*/target` + `.worktrees/*/target`) reclaimed ~27G, moving `/home` from 100% used with 86M free to 95% with 47G free. Left `~/Projects/lastfm-edit/target` (17.4G) intact deliberately: it was in active use by the running session/build and a concurrent agent, and enough space had already been freed. Lesson: when only ~80M is free, disk-write failures surface as nondeterministic Rust build errors ("could not compile … due to 1 previous error" with no diagnostic text, `disk I/O error` on `~/.cache/nix/fetcher-cache-v4.sqlite`, and openssl-sys build-script failures) rather than obvious "No space left" messages.
 
 ## Step 5: `/nix/store` Deep Dive