zhTW: translate 22 keys and correct the Delves wording

[LoChinAn]

Only Locales/zhTW.lua is touched: 25 lines added, 3 rewritten in place. 22 keys.

New keys from #1170 (9)

Four of them are whole sentences that replaced .. chains whose fragments were
already translated, so the new entries reuse that wording verbatim:

new key	wording reused from
You may only have %1$d windows active	"You may only have " + " windows active"
%1$s's Death Recap	"'s Death Recap"
%1$s's %2$s Breakdown	" Breakdown"
Overall %1$s	"Overall Deaths"

The other five: Hide in Delves and Hide in PvP follow the
Hide in Dungeons / Hide in Raids entries sitting next to them in the same
window menu; (middle click to remove) follows the existing
(Middle Click to Add or Remove); and the two Mythic+ death lines share one
translation because Chinese has no plural form.

The superseded fragment entries are left in place for now — the tail
fragments of those chains never reached the catalog either, so removing the
whole dead set is a separate pass.

Older gaps a full-tree scan turned up (13)

These predate this batch. All of them sit in dropdown or segmented-control
value tables whose siblings are already translated, so each rendered as the
lone English entry in an otherwise translated list:

• Damage (DPS) — next to DPS / Damage / Damage | DPS
• Left (Top), Right (Bottom) — the CDM Show Icon dropdown
• When Any Present, When All Present, When Any Missing,
  When All Missing — the Buff Manager Show When dropdown
• Single, Form specific — the druid power bar mode switch
• Clean (Flat) — the absorb style list, next to the stripe set
• Favor — the bar label list, next to Micro / Bags / XP / Rep

Beacon Reminders is a module title and matches AuraBuff Reminders beside
it. Sporefall is the Midnight raid — the zhTW client renders it 孢子之殞,
the same source the neighbouring The Voidspire and The Dreamrift entries
came from.

Delves wording (3 lines rewritten)

探掘 does not appear anywhere in the client's zhTW GlobalStrings; the
official rendering is 探究 (DELVES_LABEL), 探究夥伴
(DELVES_COMPANION_LABEL) and 探究旅程 (DELVES_REPUTATION_BAR_TITLE).
Corrected: Delves Companion, Delver's Journey, and the non-tank threat
shadow-border description.

Notes for reviewers

%1$d Death -%2$s / %1$d Deaths -%2$s keep the two spaces before the
dash exactly as the English keys have them.

The variable wraps in #1170 (L(group.header), L(entry.label),
L(ind.name), L(CAT_VALUES[cat])) were checked separately by resolving
each table they read from: all 47 values already have zhTW entries.

Two things the scan flagged that are deliberately not translated here:

• Control in the Spell ID Use Modifier dropdown. Shift and Alt beside
  it are intentionally left as-is, so renaming just this one would be a wording
  change rather than a translation.
• The 37 class cast-spell names in EUI_UnitFrames_Options.lua. They are
  lookup keys for C_Spell.GetSpellInfo() and the preview cast bar prints
  _previewCastSpell.name without L(), so a locale entry would have no
  effect. Worth a source-side fix rather than a locale one.