Fix TOML roundtrip: use TomlInline flag instead of FlowStyle to preserve inline tables

FlowStyle affected YAML decode output (causing inline tables to appear as
YAML flow mappings). Replace it with a new TOML-specific TomlInline bool
on CandidateNode that:
- Is set by the TOML decoder for inline tables (not FlowStyle)
- Is copied by UpdateAttributesFrom so it survives DeeplyAssign merges
- Is checked by the TOML encoder alongside FlowStyle (for YAML flow maps)
- Has no effect on the YAML encoder, preserving existing TOML→YAML output

TOML roundtrip tests are restored to their original expected values (inline
tables stay inline, table sections stay as sections).

Agent-Logs-Url: https://github.com/mikefarah/yq/sessions/f59bdf62-6d16-4664-991b-38eb87c9d81c

Co-authored-by: mikefarah <1151925+mikefarah@users.noreply.github.com>

pkg/yqlib/doc/usage/toml.md

@@ -153,9 +153,7 @@ yq '.' sample.toml
 ```
 will output
 ```yaml
-[name]
-first = "Tom"
-last = "Preston-Werner"
+name = { first = "Tom", last = "Preston-Werner" }
 ```
 
 ## Roundtrip: table section
@@ -374,10 +372,7 @@ dob = 1979-05-27T07:32:00-08:00
 enabled = true
 ports = [8000, 8001, 8002]
 data = [["delta", "phi"], [3.14]]
-
-[database.temp_targets]
-cpu = 79.5
-case = 72.0
+temp_targets = { cpu = 79.5, case = 72.0 }
 
 # [servers] yq can't do this one yet
 [servers.alpha]