ci: update size-check workflow to generate mock size report

[bukepo]

No description provided.

[gemini-code-assist]

Caution

The consumer version of Gemini Code Assist on GitHub has been sunset. All code review activity has officially ceased.

[github-actions]

Merging #25 into main

name	branch	text	data	bss	total
ot-cli-ftd	00000000	481576	860	66532	548968
	00f8515	481600	860	66540	549000
	+/-	+24	+0	+8	+32
ot-ncp-ftd	00000000	446980	764	61768	509512
	00f8515	447004	764	61776	509544
	+/-	+24	+0	+8	+32
ot-cli-mtd	00000000	373832	764	50932	425528
	00f8515	373824	764	50932	425520
	+/-	-8	+0	+0	-8
ot-ncp-mtd	00000000	355204	764	46200	402168
	00f8515	355196	764	46200	402160
	+/-	-8	+0	+0	-8
ot-cli-ftd-br	00000000	593016	864	130684	724564
	00f8515	592992	864	130684	724540
	+/-	-24	+0	+0	-24
ot-rcp	00000000	63840	568	20828	85236
	00f8515	63840	568	20828	85236
	+/-	+0	+0	+0	+0

Library files

name	branch	text	data	bss	total
libopenthread-ftd.a	00000000	251502	95	40311	291908
	00f8515	251530	95	40319	291944
	+/-	+28	+0	+8	+36
libopenthread-cli-ftd.a	00000000	61777	0	8091	69868
	00f8515	61777	0	8091	69868
	+/-	+0	+0	+0	+0
libopenthread-ncp-ftd.a	00000000	33359	0	5948	39307
	00f8515	33359	0	5948	39307
	+/-	+0	+0	+0	+0
libopenthread-mtd.a	00000000	171055	0	24743	195798
	00f8515	171039	0	24743	195782
	+/-	-16	+0	+0	-16
libopenthread-cli-mtd.a	00000000	41482	0	8059	49541
	00f8515	41482	0	8059	49541
	+/-	+0	+0	+0	+0
libopenthread-ncp-mtd.a	00000000	25783	0	5948	31731
	00f8515	25783	0	5948	31731
	+/-	+0	+0	+0	+0
libopenthread-ftd-br.a	00000000	363648	99	104423	468170
	00f8515	363628	99	104423	468150
	+/-	-20	+0	+0	-20
libopenthread-cli-ftd-br.a	00000000	80892	0	8131	89023
	00f8515	80892	0	8131	89023
	+/-	+0	+0	+0	+0
libopenthread-rcp.a	00000000	9946	0	5060	15006
	00f8515	9946	0	5060	15006
	+/-	+0	+0	+0	+0
libopenthread-radio.a	00000000	20675	0	262	20937
	00f8515	20675	0	262	20937
	+/-	+0	+0	+0	+0