Harden zenmonitor, add non-blocking sampling, headless CLI, and rolling averages

[HonsW]

Consolidated set of improvements, developed and verified incrementally. Bumps the version to 1.5.0.

Verification note: runtime sensor values require an AMD Zen host and couldn't be confirmed in the build environment. Everything builds clean (-O2 -Wall, both binaries), and the pure logic (averaging math, substring filter) was unit-checked against brute-force references. The streaming CSV's crash-safety was verified by kill -9 mid-run.

Correctness & safety

• cpu_model(): fix a 1-byte stack buffer overflow (model[48] → model[49]).
• zenpower_init(): check the hwmon name read and reset the buffer after free — avoids a NULL deref / use-after-free.
• get_core_fid(): guard against divide-by-zero when the FDID field is 0.
• malloc→g_malloc; sprintf→snprintf; drop dead code + a typo in get_core_count(); fix a signed/unsigned comparison and a shadowed counter in sysfs.c; free the leaked cpu_model() result in the GUI; convert K&R () prototypes to explicit/(void); make file-local sensor arrays static.

CPU support

• Accept family 0x19 (Zen 3 / Zen 4) alongside 0x17, matching the established zenmonitor3 fork (RAPL/energy/FID logic unchanged).

UI responsiveness & refresh interval

• Remove the blocking usleep(100ms) from msr_update(). RAPL power is now measured over the real elapsed time between refreshes (monotonic clock), so the GTK main loop is no longer frozen ~⅓ of each cycle.
• Runtime-configurable refresh interval: a header-bar button opens an "Update Interval" dialog (50–60000 ms), and --interval/-i sets the initial value (default 1000 ms). Not persisted — all configuration stays on the command line. Changing the interval re-parses the average windows for the new cadence and resets the average history (samples from different cadences can't share a window).

Headless CLI (zenmonitor-cli)

• Split the shared core into zenmonitor-lib.c; add a CLI build with stdout output, --delay (clamped to ≥ 0.05 s), --coreid, --refresh-in-place (ncurses), and --output-once. makefile gains build-cli/install-cli/all; also drops DESTDIR from the .desktop Exec path.
• --file streams a CSV log: header once, one row appended + flushed per refresh. Memory use is constant regardless of run length or sample rate, tail -f works on the live file, and the log survives up to the last row on crash/SIGKILL — suitable for long high-frequency captures. Fails fast if the file can't be opened; warns that it's ignored in --daemon mode.
• Signal handler only sets a flag (teardown runs in the main loop).

Rolling averages

• Optional GUI columns via --average (e.g. 30s,1m,5m), backed by a central ring-buffer + running-sum engine (exact windowed mean, O(windows)/tick). --average-only restricts which sensors are averaged. Omitting either keeps the original behavior.
• CLI --daemon keeps history resident and atomically rewrites a snapshot file each interval (default under $XDG_RUNTIME_DIR, i.e. tmpfs/RAM), so short-lived readers (e.g. an xfce4-genmon panel) can show a trailing average. --sensors limits which sensors are handled and skips a backend's per-tick reads when nothing matches. Example genmon script and systemd user unit under data/.

The averaging math and the substring filter live once in zenmonitor-lib.c, shared by the GUI and CLI.

Docs & housekeeping

• README documents all new options; the clone URL and the About dialog now point at this repository (original-author credit unchanged); the AUR section (which packages the upstream project) was dropped.

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