format: a log can be six shapes, and it knows what time it is

[donislawdev]

Adds entry_format to the log format - apache-combined (the default, unchanged), apache-common, nginx, syslog, plain, json-lines - and six settings beside it: timestamps, rate, methods, status_mix, ip_version, line_ending.

The text group had no settings at all until now, so this is the first, and the shape the rest will copy.

Measured, not remembered

Every template came from a real file, and two would have been wrong otherwise:

shape	what measuring corrected
nginx	its default log_format ends with $http_x_forwarded_for, so a real line carries one more quoted field than "combined"
apache	the image's own default is common - no referrer, no agent
syslog	a file carries no <PRI> - that is on the wire - and no RFC 3164 style line exists on this machine, so ISO is what a tester sees

Sources and samples: docs/MVP-FORMATS.md §5.1a.

Breaking, with a way back that is pinned

The clock advances now, one second apart by default. That moves the bytes of every log, so it is under ### Breaking with the version untouched - the animated GIF's pattern.

timestamps=fixed reproduces the old file to the byte, and there is a hash for it rather than a promise: the value log_8kib carried before this change is now pinned as log_8kib_the_way_back.

The oracle now detects the shape

It is handed a format id and a path, never a recipe - so it takes the shape from the first entry and holds every line to that one. Asking each line only to be valid on its own would pass a file that changed shape half way down.

Five deliberate breakages, five caught: truncated line, two shapes in one file, mixed endings, missing final newline, octet above 255. JSON lines goes through Python's own json module, giving this format its first reader that is not a regular expression of ours.

Three defects found after the code was written

A window could not produce syslog or JSON lines at all. A menu cannot be empty - it opens on its declared default - so a window sends every setting it draws. The first version refused a setting that could do nothing whenever the key arrived. The command line never showed it, because there an unset flag is an absent key, and every test I had written used the command line's shape of a request. Reported from a screenshot.

The folded summary line listed the format's whole declaration rather than what anybody chose, for the same reason. Unnoticed while formats declared one or two settings; with seven it ran off the edge of the window. Boxes people type into are left alone - there an empty box and a typed default genuinely differ (defaulted, untouchable rule 5).

syslog missed its size in about one file in ten. The line counted its process id as four digits always, and it runs from 100 to 9998. Only the last entry is built to a length, so the miss needed that entry to draw a short pid. Measured before the repair: 35 files out of 360 - and this project's own size guard could not see it, because it asks each format with its settings left alone, which for this one is apache-combined.

Guards

Nine mutations, all caught, including one per defect above. New guards: every shape hits its size across seeds, every shape is reachable when every setting is sent the way a window sends them, the clock advances by exactly one tick per entry, the way back holds one instant, an impossible pair is refused naming both halves, the label is a line its own reader accepts, and the folded line names what was chosen.

.gitignore gains /tfg-out/ - the window proposes it by default, so running the program from a checkout was filling the repository with generated files.