v3.26.0: per-TAR default keysets (the preset/SCP80/RAM rework)

Every preset TAR entry carries `keyset` (int 1-15) - the keyset every
operation addressed to that TAR uses: mandatory for any non-zero MSL
(the counters are keyset-linked), optional for MSL 00 (allowed: some
cards reject the no-security 00/00 KIc/KID form).  The store fills it
automatically when the preset has a single keyset, the validation
refuses an entry naming an undefined keyset, and the schema is 6 (a v5
file loads leniently; editing it forces the fix).

The keyset selectors are gone: the SCP80 TAR field became a select of
the preset's entries (applying the TAR's keyset to the form and seeding
the SPI1 from its MSL); the RAM operations use the preset's ISD role
entry (the PWA sends only the preset id, the ISD TAR, SPI and the
counter override - the server resolves the keyset and the keys:
presets.tar_keyset, _preset_tar_keyset, _resolve_operation_keyset,
_op_keyset, used by send-ota's APDU path, ram-install, ram-install-app
and cap-compat); the counter probe and the test runner's scp80 steps
default to their TAR's keyset (an explicit kvn stays an override).  A
security TAR without a keyset refuses the operation ("set it in the
Cards tab") - never a silent keyless send - and the start buttons wait
for a usable operation-TAR keyset.

The TAR probe checks the preset's TAR list only (the standard
TAR_PROBE_TARS list and the custom-TAR localStorage are gone; a `tars`
list selects a subset, a TAR outside the preset is refused), each row
using its own MSL and default keyset.  The Cards editor's TAR table
gained a Keyset column (the only keyset preselected, an amber marker
when a security MSL lacks one).

Docs: help EN/RU, api.md's tar-probe contract, both AGENTS.  Tests: the
store (the field, the auto-fill, the schema, the string forms), the
server resolution (send-ota + the refusal, the probe's per-row keysets
and refusals), the PWA (the TAR select, the RAM ISD resolution, the
keyset-free requests) - several fixtures updated for the new schema.
891 frontend + 885 Python; sw cache simple-v434.

pyproject.toml

@@ -4,7 +4,7 @@ build-backend = "setuptools.build_meta"
 
 [project]
 name = "pysim-simple-server"
-version = "3.25.8"
+version = "3.26.0"
 description = "HTTP REST server wrapping pysim for the SIMple PWA"
 requires-python = ">=3.8"
 # pysim is a git-only dependency installed explicitly by setup.bat/setup.sh.