Fix remaining disassembly regex search quirks ##search

[trufae]

Fixes #26176.

The ARM64 example in the issue still failed when its regex was quoted as an argument. Investigation also reproduced missed overlapping matches across read blocks, incorrect bytewise continuation, silent truncation of long patterns, splitting inside regex character classes, and errors reported as successful shell commands.

Keeps /ad in the legacy handler. Uses the existing r_str_unquote helper for whole-pattern arguments, accepts whitespace consistently with cmdctx, and preserves regex backslashes. Existing whole-command quoting, leading-quote calls and escaped instruction separators remain covered.

Commit	Change
50c9ea8	Accept single/double quoted patterns and tab-separated arguments; document usable regex examples.
b9d9770	Track the scan address across buffer refills so retries and bytewise sequences keep all overlapping hits. Removes the block-local retry helper.
b3f2198	Consume the final supported instruction pattern and reject more than 1023 expressions instead of returning partial false matches.
75a4a94	Preserve semicolons inside bracket expressions, including POSIX classes, collating symbols and equivalence classes.
82d1a79	Return failure for missing patterns, invalid modifiers/regexes and excess instructions; stop after the first failed map. Successful searches with zero hits still succeed.

Adds 11 r2r cases to test/db/cmd/cmd_search_ad, including the original ARM64 bytes. Ten fail against unmodified master; the additional case protects alignment/maxhits behavior. Production code changes total +95/-47 lines (net +48); tests add 213 lines.

Validation on Linux:

• Built and installed after rebasing onto dd4b271.
• 209 tests across cmd_search, cmd_search_ad, cmd_search_asm, cmd_search_in, cmd_search_hit, cmd_search_esil, shell, and feat_quote: 208 pass, zero unexpected failures. The existing Rop search w/ branch delay (mips) remains marked BROKEN.
• All 28 disassembly-search tests pass.
• python3 sys/lint.py --all and git diff --check pass.