Overhaul parquet viewer: full encoding support + rich navigation

[nwoolmer]

Summary

Fixes the original motivating bug (VARCHAR columns encoded with DeltaLengthByteArray / DeltaByteArray rendered as empty cells because everything was decoded as PLAIN) and turns the parquet viewer into a real interactive TUI.

Decoder — full encoding coverage

decode_data_page now dispatches on every Encoding variant exposed by parquet2:

• Plain, PlainDictionary, RleDictionary (existing)
• DeltaLengthByteArray, DeltaByteArray, DeltaBinaryPacked (new)
• Rle for BOOLEAN — handles V1 4-byte length prefix vs V2 (new)
• BitPacked — falls through to PLAIN; only realistic use is BOOLEAN (new)
• ByteStreamSplit for FLOAT/DOUBLE/INT32/INT64/FixedLenByteArray (new)

Decoder correctness fixes

• INT96 Julian-day math guarded with checked_mul/checked_add
• Timestamp { is_adjusted_to_utc } honored with a trailing Z
• Subsecond precision preserved (ms/µs/ns tails, trim trailing zeros)
• New format_time_of_day for Time logical type (HH:MM:SS[.frac])
• Repeated columns (max_rep_level > 0) emit an explicit marker instead of silently misaligned per-element output
• Control characters sanitized at decode time (\n preserved for row-detail popup; \t/\r/other become space/? so the terminal can't reinterpret them and break column alignment)
• Unicode display width used everywhere a column width is measured

Table view — interactive TUI

• Row + column cursor, row-number gutter with selection marker, horizontal scroll indicators (◄ / ►)
• Cell, row, and column-info popups (Enter, Shift+Enter, i)
• Regex search with wrap + per-cell match highlighting; works in both tree and table; * / # search current cell; / empty accept clears
• Row selection (Space / a, Ctrl+A, Ctrl+I) with selection-aware CSV/NDJSON export
• Clipboard: y cell, Y row TSV, c column, j row JSON
• Column ergonomics: freeze (f), hide/show (h/H), width (w/W/=/~), first/last (^/$), page (Shift+←/→), alignment (numeric right-aligns), thousands separators (,)
• In-window sort (s); canonical row id preserved in gutter
• Mouse click positions cursor; mouse wheel scrolls
• Reload (R) preserves cursor/selection/widths/hidden/frozen/sort by column name so schema drift doesn't dislodge UI state

Tree view additions

• Dictionary contents (lazy-loaded per column chunk)
• INT96 / FixedLenByteArray statistics
• Column byte offsets (data page, dict page, index page)
• Pretty-printed JSON in cell popup when value is valid JSON

Sliding-window table buffer

• TABLE_BUFFER_ROWS raised from 1k → 10k
• load_table_window does page-level skip before decoding when the requested slice starts past a page boundary
• Window recenters on the cursor on reload

Exports

• e current row group → CSV
• E full file → CSV (row-group-at-a-time streaming writer)
• J full file → NDJSON
• Selection-aware: filename includes .selected when active, and row groups with no selected rows are skipped before decode

Tests

997 total, up from 120 pre-change. Covers all new encoding decoders via parquet2's own encoders (round-trip), sanitization, Unicode-width math, alignment classifier, subsecond timestamp rendering, time-of-day, CSV/JSON quoting, regex search, thousands separators, hidden-col navigation, sort comparator, and mouse-click hit-testing.

Help dialog updated with every new key binding.

Test plan

• Open a parquet file with DeltaLengthByteArray / DeltaByteArray VARCHAR columns — cells render populated, not empty
• Open a file with BOOLEAN columns (RLE and BitPacked paths)
• Open a file with ByteStreamSplit-encoded FLOAT/DOUBLE
• INT96 and subsecond timestamp columns render with correct precision and Z suffix where applicable
• Table view: cursor movement, search (/, *, #), row selection, clipboard ops, freeze/hide/width adjust, sort (s), reload (R) preserves state
• Exports: e, E, J with and without selection; .selected appears in filename when active
• Cell popup pretty-prints JSON when value is valid JSON
• cargo test — all 997 pass
• cargo clippy --all-targets -- -D warnings clean

🤖 Generated with Claude Code

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Review follow-ups (commits 1fd2df1 → 7e99ec4)

Blockers fixed

• cargo fmt --check clean (was 42 diffs)
• cargo clippy --all-targets -- -D warnings clean (was 15 errors: useless .into_iter(), manual Iterator::find, clamp-like pattern, ?-operator, .is_multiple_of(), too-many-args → grouped into ColLayout / DataRowCtx structs)
• 21 new hardcoded Color:: references routed through Theme via 7 new fields (parquet_gutter_fg, parquet_cursor_gutter_fg, parquet_cursor_row_bg, parquet_cursor_cell_bg, parquet_selected_row_fg, parquet_indicator_fg, parquet_popup_cont_fg); both far_manager and questdb_dark palettes populated
• Popup frame now uses dh::render_dialog_frame() instead of a hand-rolled Block::default() + manual Rect centering + buf.cell_mut() clearing
• TableSearch holds a TextInput (was a raw String), so the search prompt inherits undo/redo, selection and clipboard paste like every other dialog

Warnings fixed

• Compiled regex cached on TableSearch keyed by query text; search_regex() call hoisted out of the per-row render loop (was recompiling ~N times per keystroke when search active)
• Extracted compile_search_regex() helper — was duplicated 3× across search_jump, search_tree_jump, search_regex
• Extracted pick_unused_export_path() helper — the 1000-attempt file-collision loop was duplicated 3× across CSV / full-CSV / NDJSON exports; magic 1000 is now EXPORT_ATTEMPT_LIMIT
• map_parquet_key Ctrl branch no longer swallows unmatched Ctrl chords (Ctrl+C etc. can now fall through instead of returning Action::None)
• Removed write-only TableSearch::last_match_row field (dead code)

Bug fixed during follow-up testing

• Pressing / in Tree view silently opened the search input but the hardcoded Tree hint bar never reflected the search state, so typing characters were captured into an invisible prompt. render_tree now shows the live /query prompt (and status messages) when search is active, matching Table-view behavior.

Verification

• cargo fmt --check ✓
• cargo clippy --all-targets -- -D warnings ✓
• cargo test — all 997 pass ✓