[danyill]

Fixes #171. Stacked on #151 (lazy Data Tables cell widgets): merge #151 first.

What it adds

• A per-column filter strip inside the table's own header, hidden until asked for (Ctrl+F on the table, or the header's right-click menu 'Filter rows'). No layout changes, so it lines up with the columns and follows resizing and scrolling.
• Only for tables with more than 10 rows (MIN_FILTER_ROWS); small tables get nothing.
• Expressions (pure Python, raptor/gui/table_filter.py): text (contains), Pump* / ? wildcards, "quoted phrase", !not, =exact, > >= < <= !=, 5..10, blank / nonblank; space = AND, | or , = OR. Numbers compare the cell's raw value when it has one, else the number in its text (commas, %, '>' censor mark, units ignored). A bad expression never raises: the box turns red, rows stay unfiltered.
• Typing is debounced (150 ms). A pass hides rows with setRowHidden, copies no data: 30,000 rows filter in about 0.1 s. A 'Showing N of M / Clear' note appears while a filter is active.

Where

• Results tables (_make_table: capacity, weak links, costs, importance) and the analytic per-element table.
• Data Tables (Blocks, Nodes, Events, Sparing, PM): the Blocks and Sparing filters read the model objects the rows were filled from, so hidden rows never build their cell widgets and widget columns (distribution, parameters, PM frequency) can be filtered. Sparing filters Name, ID and Sparing Type only; its other columns are widgets with no model text, so their boxes are disabled. CSV export reads only visible rows and its dialog title says 'only the N of M rows the filter shows'. An edited row that stops matching stays visible until the next time the user types in a filter box.
• Not changed: the event log (already has its own model-based filter), Phases and the other small tables. Mass Edit works on the canvas selection, not on table rows, so there is nothing to scope.

Tests: 54 expression tests, 15 for the bar, results hook and Data Tables.