B2view improvements: CTable filtering is here!

[FrancescAlted]

Many improvements in navigation for the data panel. Now it is possible to do complex filters on ctable objects.

In detail:

b2view: packaging & defaults

• b2view ships with blosc2 by default — textual/rich moved into core dependencies and the [tui] extra was removed; new "Command line tools" section in the README and a full getting-started walkthrough (doc/getting_started/b2view.rst: sample store, panels, key reference, dim mode, CLI options).
• The terminal owns the mouse by default, so native text selection/copy works; --mouse opts into capture (click-to-focus, wheel scrolls the data grid by half a page, paging at the edges).

Data panel: filtering (the headline feature)

• f — row filtering for CTables: takes the same string expressions as CTable.where() (dotted nested names, and/or) and pages through the matching view; verified on the 24.3M-row chicago-taxi store (67 matches, instant).
• / — column filtering: narrows visible columns by case-insensitive substring; column paging and the c goto-column modal operate on the subset.
• Filters combine freely, persist per node for the session, show in the data header with unfiltered totals, and escape clears one layer per press (dim mode → rows → columns).

Data panel: rendering & navigation

• Adaptive column fit: two-pass measured-width column windows replacing a fixed chars/column estimate, with re-fit on terminal resize and panel maximize/restore.
• Aligned float formatting: uniform decimals per column so decimal points line up.
• Navigation keys: c goto-column (index, exact name, or unique prefix), s/e first/last column window, cursor column preserved across row paging/jumps, and dim-mode movements now clamp at boundaries instead of wrapping.
• ? help screen listing all keys grouped by area, plus the data-panel hint bar (filter: f(rows) /(cols) | rows: t/b/g | cols: s/e/c).

Testing & housekeeping

• First automated test suite for b2view: Pilot-driven keyboard journeys against a deterministic generated store (tui marker), plus render unit tests — 11 tests total, all passing.
• A CTable regression test (sort_by on an unprojected view must not gather all columns), todo/b2view.md tracker with done/pending items, and updated install docs (pip install . --group test).